[clang] [clang][Darwin] Remove legacy framework search path logic in the frontend (PR #138234)

[Ian Anderson via cfe-commits]

ian-twilightcoder wrote:

I tried `GTEST_SHUFFLE=0 GTEST_TOTAL_SHARDS=96 GTEST_SHARD_INDEX=67 ./AllClangUnitTests` and that also passes. There's a leak from the new `SearchPathTest`, maybe that's making the address sanitizer mad?

https://github.com/llvm/llvm-project/pull/138234