[clang] [clang-tools-extra] [clang] improve class type sugar preservation in pointers to members (PR #130537)

[Matheus Izvekov via cfe-commits]

mizvekov wrote:

A dependent PR had been merged meanwhile, and this was not rebased.

While this patch is still big, you might have been seeing way more stuff than was actually in the PR.

I just rebased, but have not addressed any comments yet.

https://github.com/llvm/llvm-project/pull/130537