gh-106242: Fix path truncation in normpath

[finnagin]

Following the suggestion from this comment in the original issue this PR adds a new function _Py_normpathAndSize which behaves like _Py_normpath but also takes a pointer which it will use to store the length of the final normalized path. This new function is then used in os__path_normpath_impl to pass the above mentioned length into PyUnicode_FromWideChar instead of -1.

Additionally, this adds a test to check that normpath is not truncating paths containing a null character as well as changes test_addpackage_import_bad_pth_file in test_site.py which was using a null character to make a bad path, specifically it was using the string 'abc\x00def'. The problem is that before this change this was being truncated for parts of the test so the string it was actually using in those parts was 'abc'. Upon making the normpath changes it started throwing the error ValueError: embedded null character so I changed the test to use 'abc<>$$**:://def' instead.

• Issue: os.path.normpath truncates input on null bytes in 3.11, but not 3.10 #106242

[zooba]

LGTM with the minor name convention update

[zooba]

Looks like we just need the NEWS entry - click "Details" next to the failed check for info on it (or run PCbuild/blurb.bat to create it locally).

Text should be something like ``Fixes :func:os.normpath to handle embedded null characters without truncating the path.` and put it under Library.

[miss-islington]

Thanks @finnagin for the PR, and @zooba for merging it 🌮🎉.. I'm working now to backport this PR to: 3.11.
🐍🍒⛏🤖

[miss-islington]

Thanks @finnagin for the PR, and @zooba for merging it 🌮🎉.. I'm working now to backport this PR to: 3.12.
🐍🍒⛏🤖

[miss-islington]

Sorry, @finnagin and @zooba, I could not cleanly backport this to 3.11 due to a conflict.
Please backport using cherry_picker on command line.
cherry_picker 09322724319d4c23195300b222a1c0ea720af56b 3.11

[miss-islington]

Sorry, @finnagin and @zooba, I could not cleanly backport this to 3.12 due to a conflict.
Please backport using cherry_picker on command line.
cherry_picker 09322724319d4c23195300b222a1c0ea720af56b 3.12

[bedevere-bot]

GH-107981 is a backport of this pull request to the 3.12 branch.

[bedevere-bot]

GH-107982 is a backport of this pull request to the 3.11 branch.