Fix regex `get_data_files` formatting for base paths

With this pr https://github.com/huggingface/datasets/pull/6309, it is formatting the entire base path into regex, which results in the undesired formatting error `doesn't match the pattern` because of the line in `glob_pattern_to_regex`: `.replace("//", "/")`:
- Input: `hf://datasets/...`
- Output: `hf:/datasets/...`

This fix will only convert the `split_pattern` to regex and keep the `base_path` unchanged.

cc @albertvillanova hopefully this still works with your implementation

_The documentation is not available anymore as the PR was closed or merged._

> The reason why I used the the glob_pattern_to_regex in the entire pattern is because otherwise I got an error for Windows local paths: a base_path like 'C:\\Users\\runneradmin... made the function string_to_dict raise re.error: incomplete escape \U at position 2

What is the expected inputs and outputs for the windows `base_path`

> That issue was fixed once we pass the base_path as POSIX.

I'm not sure what you meant by that, are there still changes needed?


We took the liberty of continuing this PR to include it in today's patch release :)
I hope you don't mind

<details>
<summary>Show benchmarks</summary>

PyArrow==8.0.0

<details>
<summary>Show updated benchmarks!</summary>

### Benchmark: benchmark_array_xd.json

| metric | read_batch_formatted_as_numpy after write_array2d | read_batch_formatted_as_numpy after write_flattened_sequence | read_batch_formatted_as_numpy after write_nested_sequence | read_batch_unformated after write_array2d | read_batch_unformated after write_flattened_sequence | read_batch_unformated after write_nested_sequence | read_col_formatted_as_numpy after write_array2d | read_col_formatted_as_numpy after write_flattened_sequence | read_col_formatted_as_numpy after write_nested_sequence | read_col_unformated after write_array2d | read_col_unformated after write_flattened_sequence | read_col_unformated after write_nested_sequence | read_formatted_as_numpy after write_array2d | read_formatted_as_numpy after write_flattened_sequence | read_formatted_as_numpy after write_nested_sequence | read_unformated after write_array2d | read_unformated after write_flattened_sequence | read_unformated after write_nested_sequence | write_array2d | write_flattened_sequence | write_nested_sequence |
|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 0.007109 / 0.011353 (-0.004244) | 0.004209 / 0.011008 (-0.006799) | 0.097401 / 0.038508 (0.058892) | 0.079532 / 0.023109 (0.056423) | 0.341300 / 0.275898 (0.065402) | 0.402165 / 0.323480 (0.078685) | 0.005838 / 0.007986 (-0.002148) | 0.003310 / 0.004328 (-0.001018) | 0.072804 / 0.004250 (0.068553) | 0.059418 / 0.037052 (0.022366) | 0.339277 / 0.258489 (0.080788) | 0.418495 / 0.293841 (0.124654) | 0.035975 / 0.128546 (-0.092571) | 0.008101 / 0.075646 (-0.067546) | 0.339236 / 0.419271 (-0.080035) | 0.059326 / 0.043533 (0.015794) | 0.326880 / 0.255139 (0.071741) | 0.393614 / 0.283200 (0.110414) | 0.025830 / 0.141683 (-0.115852) | 1.657726 / 1.452155 (0.205571) | 1.817250 / 1.492716 (0.324534) |

### Benchmark: benchmark_getitem\_100B.json

| metric | get_batch_of\_1024\_random_rows | get_batch_of\_1024\_rows | get_first_row | get_last_row |
|--------|---|---|---|---|
| new / old (diff) | 0.256015 / 0.018006 (0.238008) | 0.482447 / 0.000490 (0.481957) | 0.012166 / 0.000200 (0.011966) | 0.000343 / 0.000054 (0.000288) |

### Benchmark: benchmark_indices_mapping.json

| metric | select | shard | shuffle | sort | train_test_split |
|--------|---|---|---|---|---|
| new / old (diff) | 0.029898 / 0.037411 (-0.007514) | 0.088218 / 0.014526 (0.073692) | 0.102353 / 0.176557 (-0.074203) | 0.165863 / 0.737135 (-0.571272) | 0.100342 / 0.296338 (-0.195996) |

### Benchmark: benchmark_iterating.json

| metric | read 5000 | read 50000 | read_batch 50000 10 | read_batch 50000 100 | read_batch 50000 1000 | read_formatted numpy 5000 | read_formatted pandas 5000 | read_formatted tensorflow 5000 | read_formatted torch 5000 | read_formatted_batch numpy 5000 10 | read_formatted_batch numpy 5000 1000 | shuffled read 5000 | shuffled read 50000 | shuffled read_batch 50000 10 | shuffled read_batch 50000 100 | shuffled read_batch 50000 1000 | shuffled read_formatted numpy 5000 | shuffled read_formatted_batch numpy 5000 10 | shuffled read_formatted_batch numpy 5000 1000 |
|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 0.429362 / 0.215209 (0.214153) | 4.147327 / 2.077655 (2.069672) | 2.014653 / 1.504120 (0.510533) | 1.824394 / 1.541195 (0.283199) | 1.936408 / 1.468490 (0.467917) | 0.542960 / 4.584777 (-4.041817) | 3.917215 / 3.745712 (0.171503) | 3.714825 / 5.269862 (-1.555036) | 2.180279 / 4.565676 (-2.385398) | 0.057808 / 0.424275 (-0.366467) | 0.008426 / 0.007607 (0.000819) | 0.472372 / 0.226044 (0.246327) | 4.879656 / 2.268929 (2.610728) | 2.602729 / 55.444624 (-52.841896) | 2.142593 / 6.876477 (-4.733884) | 2.206070 / 2.142072 (0.063997) | 0.635591 / 4.805227 (-4.169636) | 0.140928 / 6.500664 (-6.359736) | 0.065119 / 0.075469 (-0.010350) |

### Benchmark: benchmark_map_filter.json

| metric | filter | map fast-tokenizer batched | map identity | map identity batched | map no-op batched | map no-op batched numpy | map no-op batched pandas | map no-op batched pytorch | map no-op batched tensorflow |
|--------|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 1.455909 / 1.841788 (-0.385879) | 20.803592 / 8.074308 (12.729284) | 14.788713 / 10.191392 (4.597321) | 0.170546 / 0.680424 (-0.509878) | 0.021189 / 0.534201 (-0.513012) | 0.432368 / 0.579283 (-0.146915) | 0.444664 / 0.434364 (0.010300) | 0.517744 / 0.540337 (-0.022593) | 0.699265 / 1.386936 (-0.687671) |

</details>
PyArrow==latest

<details>
<summary>Show updated benchmarks!</summary>

### Benchmark: benchmark_array_xd.json

| metric | read_batch_formatted_as_numpy after write_array2d | read_batch_formatted_as_numpy after write_flattened_sequence | read_batch_formatted_as_numpy after write_nested_sequence | read_batch_unformated after write_array2d | read_batch_unformated after write_flattened_sequence | read_batch_unformated after write_nested_sequence | read_col_formatted_as_numpy after write_array2d | read_col_formatted_as_numpy after write_flattened_sequence | read_col_formatted_as_numpy after write_nested_sequence | read_col_unformated after write_array2d | read_col_unformated after write_flattened_sequence | read_col_unformated after write_nested_sequence | read_formatted_as_numpy after write_array2d | read_formatted_as_numpy after write_flattened_sequence | read_formatted_as_numpy after write_nested_sequence | read_unformated after write_array2d | read_unformated after write_flattened_sequence | read_unformated after write_nested_sequence | write_array2d | write_flattened_sequence | write_nested_sequence |
|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 0.007592 / 0.011353 (-0.003760) | 0.004045 / 0.011008 (-0.006964) | 0.073434 / 0.038508 (0.034926) | 0.076962 / 0.023109 (0.053853) | 0.468873 / 0.275898 (0.192975) | 0.479968 / 0.323480 (0.156488) | 0.006270 / 0.007986 (-0.001716) | 0.003652 / 0.004328 (-0.000677) | 0.069893 / 0.004250 (0.065643) | 0.061902 / 0.037052 (0.024850) | 0.443379 / 0.258489 (0.184890) | 0.492627 / 0.293841 (0.198786) | 0.035967 / 0.128546 (-0.092579) | 0.009276 / 0.075646 (-0.066370) | 0.083060 / 0.419271 (-0.336212) | 0.050870 / 0.043533 (0.007337) | 0.438246 / 0.255139 (0.183107) | 0.472074 / 0.283200 (0.188874) | 0.023724 / 0.141683 (-0.117959) | 1.677178 / 1.452155 (0.225023) | 1.732273 / 1.492716 (0.239557) |

### Benchmark: benchmark_getitem\_100B.json

| metric | get_batch_of\_1024\_random_rows | get_batch_of\_1024\_rows | get_first_row | get_last_row |
|--------|---|---|---|---|
| new / old (diff) | 0.244693 / 0.018006 (0.226687) | 0.470067 / 0.000490 (0.469577) | 0.005574 / 0.000200 (0.005374) | 0.000105 / 0.000054 (0.000051) |

### Benchmark: benchmark_indices_mapping.json

| metric | select | shard | shuffle | sort | train_test_split |
|--------|---|---|---|---|---|
| new / old (diff) | 0.036242 / 0.037411 (-0.001169) | 0.099166 / 0.014526 (0.084641) | 0.116785 / 0.176557 (-0.059772) | 0.174986 / 0.737135 (-0.562149) | 0.118130 / 0.296338 (-0.178209) |

### Benchmark: benchmark_iterating.json

| metric | read 5000 | read 50000 | read_batch 50000 10 | read_batch 50000 100 | read_batch 50000 1000 | read_formatted numpy 5000 | read_formatted pandas 5000 | read_formatted tensorflow 5000 | read_formatted torch 5000 | read_formatted_batch numpy 5000 10 | read_formatted_batch numpy 5000 1000 | shuffled read 5000 | shuffled read 50000 | shuffled read_batch 50000 10 | shuffled read_batch 50000 100 | shuffled read_batch 50000 1000 | shuffled read_formatted numpy 5000 | shuffled read_formatted_batch numpy 5000 10 | shuffled read_formatted_batch numpy 5000 1000 |
|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 0.475907 / 0.215209 (0.260698) | 4.708125 / 2.077655 (2.630470) | 2.600855 / 1.504120 (1.096735) | 2.446498 / 1.541195 (0.905303) | 2.538786 / 1.468490 (1.070296) | 0.566787 / 4.584777 (-4.017990) | 4.066187 / 3.745712 (0.320475) | 3.743632 / 5.269862 (-1.526229) | 2.337737 / 4.565676 (-2.227939) | 0.068402 / 0.424275 (-0.355873) | 0.008674 / 0.007607 (0.001067) | 0.593428 / 0.226044 (0.367384) | 5.840687 / 2.268929 (3.571759) | 3.194937 / 55.444624 (-52.249688) | 2.899033 / 6.876477 (-3.977444) | 2.977870 / 2.142072 (0.835797) | 0.683673 / 4.805227 (-4.121554) | 0.154933 / 6.500664 (-6.345731) | 0.071619 / 0.075469 (-0.003850) |

### Benchmark: benchmark_map_filter.json

| metric | filter | map fast-tokenizer batched | map identity | map identity batched | map no-op batched | map no-op batched numpy | map no-op batched pandas | map no-op batched pytorch | map no-op batched tensorflow |
|--------|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 1.501895 / 1.841788 (-0.339893) | 21.709792 / 8.074308 (13.635484) | 15.679556 / 10.191392 (5.488164) | 0.188028 / 0.680424 (-0.492396) | 0.022555 / 0.534201 (-0.511646) | 0.439840 / 0.579283 (-0.139443) | 0.452140 / 0.434364 (0.017776) | 0.526421 / 0.540337 (-0.013916) | 0.731692 / 1.386936 (-0.655244) |

</details>
</details>

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