GH-41863: [Python][Parquet] Support lz4_raw as a compression name alias

[nwoolmer]

Closes #41863

Rationale for this change

Other tools in the parquet ecosystem distinguish between LZ4 and LZ4_RAW, matching the specification: https://parquet.apache.org/docs/file-format/data-pages/compression/

LZ4 (framing) is of course deprecated. PyArrow does not support it, and instead simplifies the user-facing API, using LZ4 as an alias for the LZ4_RAW codec.

However, PyArrow does not accept LZ4_RAW as a valid alias for the LZ4_RAW codec:

ArrowException: Unsupported compression: lz4_raw

This is a friction issue, and confusing for some users who are aware of the differences.

What changes are included in this PR?

• Adding LZ4_RAW to the acceptable codec names list.
• Modifying the LZ4->LZ4_RAW mapping to also accept LZ4_RAW->LZ4_RAW.
• Adding a test

Are these changes tested?

Yes.

Are there any user-facing changes?

Yes, an additive change to the accepted codec names.

• GitHub Issue: [Python][Parquet] Support LZ4_RAW for parquet writing #41863

[AlenkaF]

Thank you for contributing @nwoolmer!
I think the changes look good. Can we add some additional text in the User Guide connected to the alias added: https://arrow.apache.org/docs/python/parquet.html#compression-encoding-and-file-compatibility? And maybe even mention alias in the updated Parquet writer docstrings?

[nwoolmer]

@AlenkaF Just checking the docs build failure. Some of the failures look unrelated to my change, but I am unfamiliar with any dependencies you might have between the pages.

[rok]

Yes, docstest failures are unrelated.