Make convert_to_parquet CLI command create script branch

Make convert_to_parquet CLI command create a "script" branch and keep the script file on it.

This PR proposes the simplest UX approach: whenever `--revision` is not explicitly passed (i.e., when the script is in the main branch), try to create a "script" branch from the "main" branch; if the "script" branch exists already, then do nothing.

Follow-up of:
- #6795

Close #6808.

CC: @severo 

Comments:
The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/datasets/pr_6809). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

@huggingface/datasets once this PR is merged, I would suggest making a release. Do you agree?
- This PR is a follow-up of #6795

<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) | 0.004963 / 0.011353 (-0.006390) | 0.003121 / 0.011008 (-0.007888) | 0.063421 / 0.038508 (0.024913) | 0.030727 / 0.023109 (0.007618) | 0.237698 / 0.275898 (-0.038200) | 0.266613 / 0.323480 (-0.056867) | 0.004237 / 0.007986 (-0.003749) | 0.002715 / 0.004328 (-0.001614) | 0.049503 / 0.004250 (0.045253) | 0.043705 / 0.037052 (0.006653) | 0.247818 / 0.258489 (-0.010671) | 0.287545 / 0.293841 (-0.006296) | 0.027232 / 0.128546 (-0.101314) | 0.009952 / 0.075646 (-0.065695) | 0.208678 / 0.419271 (-0.210593) | 0.035494 / 0.043533 (-0.008039) | 0.260900 / 0.255139 (0.005761) | 0.264738 / 0.283200 (-0.018461) | 0.018093 / 0.141683 (-0.123590) | 1.130924 / 1.452155 (-0.321231) | 1.178982 / 1.492716 (-0.313734) |

### 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) | 0.094610 / 0.018006 (0.076604) | 0.304674 / 0.000490 (0.304184) | 0.000215 / 0.000200 (0.000015) | 0.000048 / 0.000054 (-0.000007) |

### Benchmark: benchmark_indices_mapping.json

| metric | select | shard | shuffle | sort | train_test_split |
|--------|---|---|---|---|---|
| new / old (diff) | 0.018168 / 0.037411 (-0.019243) | 0.062040 / 0.014526 (0.047514) | 0.075634 / 0.176557 (-0.100922) | 0.119488 / 0.737135 (-0.617647) | 0.074790 / 0.296338 (-0.221548) |

### 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) | 0.282449 / 0.215209 (0.067240) | 2.773231 / 2.077655 (0.695576) | 1.455156 / 1.504120 (-0.048964) | 1.332652 / 1.541195 (-0.208543) | 1.340795 / 1.468490 (-0.127695) | 0.576588 / 4.584777 (-4.008189) | 2.415513 / 3.745712 (-1.330199) | 2.801569 / 5.269862 (-2.468292) | 1.741039 / 4.565676 (-2.824637) | 0.064386 / 0.424275 (-0.359890) | 0.005293 / 0.007607 (-0.002314) | 0.329732 / 0.226044 (0.103688) | 3.227275 / 2.268929 (0.958347) | 1.793121 / 55.444624 (-53.651503) | 1.515115 / 6.876477 (-5.361362) | 1.518738 / 2.142072 (-0.623335) | 0.664465 / 4.805227 (-4.140762) | 0.118813 / 6.500664 (-6.381851) | 0.041715 / 0.075469 (-0.033754) |

### 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) | 0.974371 / 1.841788 (-0.867416) | 11.432869 / 8.074308 (3.358561) | 9.607939 / 10.191392 (-0.583453) | 0.143996 / 0.680424 (-0.536427) | 0.014624 / 0.534201 (-0.519577) | 0.286899 / 0.579283 (-0.292384) | 0.265965 / 0.434364 (-0.168399) | 0.324727 / 0.540337 (-0.215611) | 0.420917 / 1.386936 (-0.966019) |

</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) | 0.005145 / 0.011353 (-0.006207) | 0.003723 / 0.011008 (-0.007286) | 0.050387 / 0.038508 (0.011879) | 0.030734 / 0.023109 (0.007625) | 0.274331 / 0.275898 (-0.001567) | 0.295045 / 0.323480 (-0.028435) | 0.004187 / 0.007986 (-0.003799) | 0.002781 / 0.004328 (-0.001547) | 0.049698 / 0.004250 (0.045448) | 0.040049 / 0.037052 (0.002996) | 0.284016 / 0.258489 (0.025527) | 0.309908 / 0.293841 (0.016067) | 0.028994 / 0.128546 (-0.099552) | 0.010625 / 0.075646 (-0.065021) | 0.059305 / 0.419271 (-0.359967) | 0.032982 / 0.043533 (-0.010551) | 0.273342 / 0.255139 (0.018203) | 0.291726 / 0.283200 (0.008527) | 0.018084 / 0.141683 (-0.123599) | 1.136864 / 1.452155 (-0.315290) | 1.163656 / 1.492716 (-0.329061) |

### 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) | 0.094868 / 0.018006 (0.076862) | 0.302900 / 0.000490 (0.302410) | 0.000226 / 0.000200 (0.000026) | 0.000053 / 0.000054 (-0.000002) |

### Benchmark: benchmark_indices_mapping.json

| metric | select | shard | shuffle | sort | train_test_split |
|--------|---|---|---|---|---|
| new / old (diff) | 0.022142 / 0.037411 (-0.015269) | 0.077457 / 0.014526 (0.062932) | 0.087989 / 0.176557 (-0.088568) | 0.127354 / 0.737135 (-0.609781) | 0.092027 / 0.296338 (-0.204312) |

### 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) | 0.291196 / 0.215209 (0.075987) | 2.840386 / 2.077655 (0.762731) | 1.571201 / 1.504120 (0.067081) | 1.449429 / 1.541195 (-0.091765) | 1.467189 / 1.468490 (-0.001301) | 0.580991 / 4.584777 (-4.003786) | 2.422566 / 3.745712 (-1.323146) | 2.839621 / 5.269862 (-2.430240) | 1.782987 / 4.565676 (-2.782689) | 0.064765 / 0.424275 (-0.359510) | 0.005338 / 0.007607 (-0.002269) | 0.349148 / 0.226044 (0.123104) | 3.421283 / 2.268929 (1.152355) | 1.943503 / 55.444624 (-53.501122) | 1.653881 / 6.876477 (-5.222596) | 1.698141 / 2.142072 (-0.443931) | 0.667628 / 4.805227 (-4.137599) | 0.118469 / 6.500664 (-6.382195) | 0.041693 / 0.075469 (-0.033776) |

### 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) | 1.026385 / 1.841788 (-0.815403) | 12.225049 / 8.074308 (4.150741) | 10.363072 / 10.191392 (0.171680) | 0.142682 / 0.680424 (-0.537742) | 0.015698 / 0.534201 (-0.518502) | 0.288148 / 0.579283 (-0.291135) | 0.272639 / 0.434364 (-0.161724) | 0.325305 / 0.540337 (-0.215032) | 0.421395 / 1.386936 (-0.965541) |

</details>
</details>

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