Add tests for os.chmod() and os.lchmod()

[serhiy-storchaka]

Currently only tests that test os.chmod() and os.lchmod() are tests that they raise exceptions for invalid arguments. There are no tests for working os.chmod() and os.lchmod() and their behavior with symlinks (there is a difference between Windows and POSIX).

Linked PRs

• gh-113086: Add tests for os.chmod() and os.lchmod() #113087
• [3.12] gh-113086: Add tests for os.chmod() and os.lchmod() (GH-113087) #113088
• [3.11] gh-113086: Add tests for os.chmod() and os.lchmod() (GH-113087) #113089