_get_name_from_path() in Lib/unittest/loader.py fails when src path contains symlinks

Bug report

Bug description:

This is conceptually somewhat similar to gh-148314

When the path to the source tree is via a symlink, an alternate path to the same will cause _get_name_from_path() to assert, thinking the supplied path is not a sub-path of the src tree. During the run of unittest's test suite, "." is passed as a path which is resolved to an absolute path - which of course doesn't match a symlinked path.

CPython versions tested on:

CPython main branch

Operating systems tested on:

macOS

Linked PRs

• gh-149143

Lib/unittest/loader.py の _get_name_from_path() から始め、その後、symlink 経由で到達するソースツリーのパスを使って unittest のテストスイートを実行します。代替パスでサブパスの assertion が発生しなくなり、関連するリグレッションカバレッジが通れば完了です。gh-149143 はすでにこの issue にリンクされています。