gh-126253: Ignore unknown Windows file attribute bits in scandir test

[Wanbinyu]

Closes #126253.

os.scandir().stat() and os.stat() can return different values for st_file_attributes when NTFS reports bits that are not exposed by Python's stat module. Limit the scandir test comparison to the public stat.FILE_ATTRIBUTE_* bits, while continuing to compare every public bit strictly.

The regression test constructs os.stat_result values with the reported 0x10000000 bit so the behavior is covered even on Windows builds where the filesystem does not naturally return it. It also verifies that a difference in FILE_ATTRIBUTE_READONLY still fails the comparison.

Tests:

• PCbuild\amd64\python_d.exe -m test test_os.test_os -m "*attributes*" -v
• PCbuild\amd64\python_d.exe -m test -v test_os
• PCbuild\amd64\python_d.exe Tools\patchcheck\patchcheck.py

This contribution was prepared with assistance from OpenAI Codex. I reviewed and tested the resulting changes.

• Issue: test_os.test_attributes() fails on Windows #126253

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