[clang] [clang][Darwin] Remove legacy framework search path logic in the frontend (PR #120149)

[Ian Anderson via cfe-commits]

ian-twilightcoder wrote:

> Unfortunately I don't have bandwidth to take this through the finish line. I just spoke with @ian-twilightcoder who said he'd try to pick it up soon (thanks a lot!).

I'm not a maintainer so I can't update this PR. I ended up needing to tweak most of it, especially where it conflicted with https://github.com/llvm/llvm-project/pull/120507. New PR is https://github.com/llvm/llvm-project/pull/138234

https://github.com/llvm/llvm-project/pull/120149