[clang] [libclang/python] Fix bug in `SourceRange.__contains__`, add tests (PR #101802)

[Vlad Serebrennikov via cfe-commits]

https://github.com/Endilll requested changes to this pull request.

Thank you, this is moving in the right direction.
You should also add an entry to potentially breaking section of release notes, because according to Hyrum's law, someone for sure depends on the current behavior of `SourceLocation.__contains__`.

https://github.com/llvm/llvm-project/pull/101802