GeezerVison

Part of #18972

Follows up on #18971, which worked around the old pyreadline in the Windows build image's pre-installed Python 3.10 but kept 3.10 in the build. This PR stops the crc32c build from using 3.10 and moves tooling jobs off it.

Changes

google-crc32c: end support for Python 3.10

• Removes 3.10.11 from scripts/python_versions.yaml, so the Windows, macOS and Linux builds no longer build 3.10 wheels. The first listed version, now 3.11, is also what the py -3 and macOS publish steps use.
• Raises the minimum to Python 3.11 in setup.cfg and pyproject.toml, and updates the classifiers, README.md and mypy.ini to match.
• Keeps unit-3.10 as a session that skips itself, because the shared CI matrix still runs it for every package. This matches how fix: drop support for end-of-life Python 3.10 #19015 handled pandas-gbq.

Tooling that doesn't need 3.10

• unittest.yml: the shard and coverage report jobs now use Python 3.14.
• main.yml: corrects a step named "Set up Python 3.10" that already installed 3.15.
• crc32c test.bat: the fallback version for manual runs is now 3.14.
• The skip-only docs and docfx sessions in google-crc32c and gcp-sphinx-docfx-yaml now use 3.15, which docs.yml installs.

For reviewers: this ends 3.10 support for crc32c

With python_requires raised, pip on Python 3.10 will install the last compatible crc32c release, so existing users keep a working install but get no new versions. Other libraries in this repo depend on crc32c and still support 3.10. Please let me know if you'd rather keep 3.10 wheels for now, and I'll limit this to the tooling changes.

Testing

Run locally on Windows:

The unit tests above use the pure-Python mode. The Kokoro wheel builds for Windows, macOS and Linux couldn't be run locally, so those need checking on this PR.

Not in this PR

Most docs and docfx nox sessions (about 300 files, plus the generator template and goldens) remain on Python 3.10, so docs.yml still installs it. I tested google-apps-card and found:

• Python 3.12 is the newest version that works, because Sphinx 4.5.0 needs the imghdr module removed in 3.13.
• On 3.11 and later, docfx output changes for enums, from Interaction(value) to a signature exposing Enum internals, such as Interaction(value, names=<not given>, *values, module=None, ...). That needs a fix in gcp-sphinx-docfx-yaml before those sessions move.

The unit test matrices and "oldest Python" jobs also stay on 3.10 while packages still declare support for it.

• Make sure to open an issue as a bug/issue before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
• Ensure the tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)