GH-49509: [Docs][Python][C++] Minimize warnings and docutils errors for Sphinx build html

[tadeja]

Rationale for this change

Closes #49509

What changes are included in this PR?

Docs formatting/typos corrected.

Are these changes tested?

Yes, on fork branch.

Are there any user-facing changes?

No, just corrected formatting/typos in docs.

• GitHub Issue: [Docs][Python][C++] Minimize warnings and docutils errors for Sphinx build html where possible #49509

[tadeja]

Reposting from the issue:

Examples of CI logs
AMD64 Conda Python 3.11 Sphinx & Numpydoc
AMD64 Debian 12 Complete Documentation
AMD64 Conda Python 3.12 Sphinx Documentation

/opt/conda/envs/arrow/lib/python3.12/site-packages/numpydoc/docscrape.py:203: UserWarning: potentially wrong underline length... 
Example 
-------- in 
...
/opt/conda/envs/arrow/lib/python3.12/site-packages/pyarrow/compute.py:docstring of pyarrow.compute.atanh_checked:4: ERROR: Undefined substitution referenced: "x". [docutils]
docstring of pyarrow.lib.BaseListArray.flatten:44: ERROR: Unexpected indentation. [docutils]
docstring of pyarrow.lib.BaseListArray.flatten:47: WARNING: Definition list ends without a blank line; unexpected unindent. [docutils]
...
/build/python/docs/source/cpp/api/cuda.rst:73: WARNING: Error when parsing function declaration
...
WARNING: unknown role name: python:mod
/build/python/docs/source/cpp/env_vars.rst:96: ERROR: Unknown interpreted text role "python:mod". [docutils]
...
/build/python/docs/source/format/Security.rst:62: WARNING: undefined label: '_format_columnar' [ref.ref]
/build/python/docs/source/format/Security.rst:173: WARNING: undefined label: '_ipc-message-format' [ref.ref]
...

[tadeja]

Most of the errors show up as malformed doc pages and correcting these improves doc page readability;

/opt/conda/envs/arrow/lib/python3.12/site-packages/pyarrow/parquet/core.py:docstring of pyarrow.parquet.core.write_table:195: ERROR: Unexpected indentation. [docutils]
/opt/conda/envs/arrow/lib/python3.12/site-packages/pyarrow/parquet/core.py:docstring of pyarrow.parquet.core.write_table:196: WARNING: Block quote ends without a blank line; unexpected unindent. [docutils]
..

https://arrow.apache.org/docs/dev/python/generated/pyarrow.parquet.write_table.html
Unintentional text boxes within malformed listings of the physical types: - int32:, - fixed_len_byte_array: , and - binary:

• min_chunk_size: and -max_chunk_size:

[tadeja]

https://arrow.apache.org/docs/dev/cpp/env_vars.html broken link, it should be
:py:mod:multiprocessing to link to Python multiprocessing

[tadeja]

Broken bool_ https://arrow.apache.org/docs/dev/python/generated/pyarrow.Bool8Array.html#pyarrow.Bool8Array.from_numpy

and malformed flatten code example

https://arrow.apache.org/docs/dev/python/generated/pyarrow.ListArray.html#pyarrow.ListArray.flatten

docstring of pyarrow.lib.Bool8Array.from_numpy:2: ERROR: Unknown target name: "bool". [docutils]
...
docstring of pyarrow.lib.BaseListArray.flatten:44: ERROR: Unexpected indentation. [docutils]
docstring of pyarrow.lib.BaseListArray.flatten:47: WARNING: Definition list ends without a blank line; unexpected unindent. [docutils]
docstring of pyarrow.lib.BaseListArray.flatten:49: ERROR: Unexpected indentation. [docutils]
docstring of pyarrow.lib.BaseListArray.flatten:51: WARNING: Block quote ends without a blank line; unexpected unindent. [docutils]
docstring of pyarrow.lib.BaseListArray.flatten:53: ERROR: Unexpected indentation. [docutils]
docstring of pyarrow.lib.BaseListArray.flatten:55: WARNING: Block quote ends without a blank line; unexpected unindent. [docutils]
docstring of pyarrow.lib.BaseListArray.flatten:56: WARNING: Block quote ends without a blank line; unexpected unindent. [docutils]
...
...