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

[Jannick Kremer via cfe-commits]

DeinAlptraum wrote:

I am closing this PR since all changes here have been implemented in other PRs:
- Additions to the `File` interface: #130383 
- Additions to the `Cursor` interface: #132377
- Type annotations: #138103

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