_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

从 Lib/unittest/loader.py 中的 _get_name_from_path() 开始，然后使用通过 symlink 到达的源代码树路径运行 unittest 测试套件。完成标准是替代路径不再触发子路径 assertion，并且相关的回归测试覆盖通过；gh-149143 已经与此 issue 关联。