Prep for Python 3.14: Rename compression to data_compression

[cclauss]

Describe your change:

Please do not merge. Blocked by:

• Help wanted: Why do maths/radix2_fft.py test results change on Python 3.14 beta? #12729
• Production release of Python 3.14 scheduled for 7 Oct 2025.

Python 3.14 will add a compression package to the Python Standard Library, which will cause our pytests to fail.

• https://docs.python.org/3.14/whatsnew/3.14.html#pep-784-adding-zstandard-to-the-standard-library
• DO NOT MERGE: Test Python 3.14 #12710

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• Rename the compression directory to data_compression
• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Add or change doctests? -- Note: Please avoid changing both code and tests in a single pull request.
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
• If this pull request resolves one or more open issues then the description above includes the issue number(s) with a closing keyword: "Fixes #ISSUE-NUMBER".