[clang] [libclang/python] Add a few things to the python api (PR #120590)

[Vlad Serebrennikov via cfe-commits]

https://github.com/Endilll commented:

Even though this PR is rather small, it is still a bunch of changes here and there. I'd prefer it to be split up into multiple focused PRs.

https://github.com/llvm/llvm-project/pull/120590