[docs] Complete `to_iterable_dataset`

Finishes the `to_iterable_dataset` documentation by adding it to the relevant sections in the tutorial and guide.


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

<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) | 0.008219 / 0.011353 (-0.003134) | 0.005201 / 0.011008 (-0.005807) | 0.108542 / 0.038508 (0.070034) | 0.076427 / 0.023109 (0.053318) | 0.441257 / 0.275898 (0.165358) | 0.436477 / 0.323480 (0.112997) | 0.006915 / 0.007986 (-0.001071) | 0.004215 / 0.004328 (-0.000113) | 0.072517 / 0.004250 (0.068267) | 0.066906 / 0.037052 (0.029853) | 0.431153 / 0.258489 (0.172664) | 0.413359 / 0.293841 (0.119518) | 0.051112 / 0.128546 (-0.077435) | 0.014664 / 0.075646 (-0.060982) | 0.358385 / 0.419271 (-0.060887) | 0.069682 / 0.043533 (0.026149) | 0.434810 / 0.255139 (0.179671) | 0.484372 / 0.283200 (0.201172) | 0.035731 / 0.141683 (-0.105952) | 1.827648 / 1.452155 (0.375494) | 2.039761 / 1.492716 (0.547045) |

### 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) | 0.277386 / 0.018006 (0.259379) | 0.599771 / 0.000490 (0.599282) | 0.005033 / 0.000200 (0.004833) | 0.000091 / 0.000054 (0.000037) |

### Benchmark: benchmark_indices_mapping.json

| metric | select | shard | shuffle | sort | train_test_split |
|--------|---|---|---|---|---|
| new / old (diff) | 0.030652 / 0.037411 (-0.006759) | 0.103435 / 0.014526 (0.088909) | 0.120072 / 0.176557 (-0.056485) | 0.177886 / 0.737135 (-0.559249) | 0.140636 / 0.296338 (-0.155702) |

### 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) | 0.603729 / 0.215209 (0.388520) | 6.144213 / 2.077655 (4.066558) | 2.785080 / 1.504120 (1.280960) | 2.368958 / 1.541195 (0.827763) | 2.409806 / 1.468490 (0.941316) | 0.836531 / 4.584777 (-3.748246) | 5.154035 / 3.745712 (1.408323) | 4.620224 / 5.269862 (-0.649638) | 2.879441 / 4.565676 (-1.686235) | 0.087322 / 0.424275 (-0.336953) | 0.007698 / 0.007607 (0.000090) | 0.678443 / 0.226044 (0.452399) | 7.431798 / 2.268929 (5.162869) | 3.589905 / 55.444624 (-51.854719) | 2.679349 / 6.876477 (-4.197127) | 3.100569 / 2.142072 (0.958496) | 1.021501 / 4.805227 (-3.783726) | 0.203150 / 6.500664 (-6.297514) | 0.073545 / 0.075469 (-0.001924) |

### 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) | 1.669981 / 1.841788 (-0.171806) | 23.379274 / 8.074308 (15.304966) | 19.811451 / 10.191392 (9.620059) | 0.197705 / 0.680424 (-0.482719) | 0.030112 / 0.534201 (-0.504089) | 0.501720 / 0.579283 (-0.077563) | 0.582413 / 0.434364 (0.148049) | 0.513261 / 0.540337 (-0.027076) | 0.729710 / 1.386936 (-0.657226) |

</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) | 0.011493 / 0.011353 (0.000140) | 0.005478 / 0.011008 (-0.005530) | 0.070955 / 0.038508 (0.032447) | 0.073877 / 0.023109 (0.050768) | 0.425765 / 0.275898 (0.149867) | 0.440869 / 0.323480 (0.117389) | 0.008322 / 0.007986 (0.000337) | 0.004004 / 0.004328 (-0.000325) | 0.071968 / 0.004250 (0.067718) | 0.060576 / 0.037052 (0.023524) | 0.448731 / 0.258489 (0.190242) | 0.517038 / 0.293841 (0.223197) | 0.051542 / 0.128546 (-0.077005) | 0.013219 / 0.075646 (-0.062427) | 0.077933 / 0.419271 (-0.341339) | 0.072879 / 0.043533 (0.029346) | 0.436553 / 0.255139 (0.181414) | 0.510050 / 0.283200 (0.226850) | 0.037136 / 0.141683 (-0.104547) | 1.535706 / 1.452155 (0.083552) | 1.611909 / 1.492716 (0.119192) |

### 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) | 0.335648 / 0.018006 (0.317642) | 0.612787 / 0.000490 (0.612297) | 0.021934 / 0.000200 (0.021734) | 0.000113 / 0.000054 (0.000059) |

### Benchmark: benchmark_indices_mapping.json

| metric | select | shard | shuffle | sort | train_test_split |
|--------|---|---|---|---|---|
| new / old (diff) | 0.028164 / 0.037411 (-0.009247) | 0.097686 / 0.014526 (0.083160) | 0.093343 / 0.176557 (-0.083214) | 0.156871 / 0.737135 (-0.580264) | 0.102694 / 0.296338 (-0.193645) |

### 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) | 0.609348 / 0.215209 (0.394139) | 5.835798 / 2.077655 (3.758144) | 2.792700 / 1.504120 (1.288580) | 2.539597 / 1.541195 (0.998403) | 2.413003 / 1.468490 (0.944513) | 0.882404 / 4.584777 (-3.702372) | 5.170564 / 3.745712 (1.424852) | 4.621663 / 5.269862 (-0.648199) | 3.029683 / 4.565676 (-1.535993) | 0.097061 / 0.424275 (-0.327214) | 0.008940 / 0.007607 (0.001333) | 0.723052 / 0.226044 (0.497007) | 7.484947 / 2.268929 (5.216018) | 3.833049 / 55.444624 (-51.611575) | 3.019606 / 6.876477 (-3.856871) | 3.270503 / 2.142072 (1.128430) | 0.977870 / 4.805227 (-3.827357) | 0.210090 / 6.500664 (-6.290574) | 0.094723 / 0.075469 (0.019254) |

### 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) | 1.585278 / 1.841788 (-0.256510) | 22.769727 / 8.074308 (14.695419) | 19.503640 / 10.191392 (9.312248) | 0.231996 / 0.680424 (-0.448428) | 0.032641 / 0.534201 (-0.501560) | 0.429833 / 0.579283 (-0.149451) | 0.549606 / 0.434364 (0.115242) | 0.527405 / 0.540337 (-0.012933) | 0.713302 / 1.386936 (-0.673634) |

</details>
</details>

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