[clang] [libclang/python] Fix some type errors, add type annotations (PR #98745)

[Nikita Popov via cfe-commits]

nikic wrote:

@DeinAlptraum It's a major change to the clang python bindings. In general, please refrain from landing major changes immediately before branching (and certainly do not backport them to the release branch).

https://github.com/llvm/llvm-project/pull/98745