gh-158169: Clear zlib.Decompress.unconsumed_tail at end of stream

[GruffElixir]

Fixes #158169.\n\nWhen decompression reaches EOF after a max_length-limited call, trailing bytes are copied to unused_data. Advance next_in past those bytes so the unconsumed_tail update clears them instead of exposing the same bytes through both attributes.\n\nAdds a regression test for limited decompression with trailing input.\n\nValidation:\n- Windows Debug build with PCbuild/build.bat\n- PCbuild/amd64/python_d.exe -m test -v test_zlib\n- PCbuild/amd64/python_d.exe -m test -R 3:2 test_zlib\n- Tools/patchcheck/patchcheck.py

• Issue: zlib: Decompress.unconsumed_tail should be cleared on eof #158169

[python-cla-bot]

All commit authors signed the Contributor License Agreement.

[miss-islington-app]

Thanks @GruffElixir for the PR, and @StanFromIreland for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖

[miss-islington-app]

Thanks @GruffElixir for the PR, and @StanFromIreland for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

[miss-islington-app]

Thanks @GruffElixir for the PR, and @StanFromIreland for merging it 🌮🎉.. I'm working now to backport this PR to: 3.15.
🐍🍒⛏🤖 I'm not a witch! I'm not a witch!

[miss-islington-app]

Sorry, @GruffElixir and @StanFromIreland, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 8122ff4818f418e8ae984cf6964215689b00808d 3.13

[miss-islington-app]

Sorry, @GruffElixir and @StanFromIreland, I could not cleanly backport this to 3.14 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 8122ff4818f418e8ae984cf6964215689b00808d 3.14

[bedevere-app]

GH-158228 is a backport of this pull request to the 3.15 branch.

[bedevere-app]

GH-158229 is a backport of this pull request to the 3.14 branch.