[clang] [libclang/python] Add equality comparison operators for File (PR #130383)

[Jannick Kremer via cfe-commits]

DeinAlptraum wrote:

@Endilll having merged #135773  and rebased, the issues with file equality for in-memory files are resolved.
I've reduced this to two tests now, that run on the except same C code except one of them uses on-disk files and the other one uses in-memory files. This replicates pretty much exactly how we test `clang_File_isEqual` on C++ side.

https://github.com/llvm/llvm-project/pull/130383