[clang] [clang] Merge gtest binaries into AllClangUnitTests (PR #134196)

[Nico Weber via cfe-commits]

nico wrote:

`BasicTests` and `FormatTests` had fairly few deps (they didn't need Sema etc) and compiled much fewer files than they presumably now do. Does it make sense to keep those as distinct binaries?

https://github.com/llvm/llvm-project/pull/134196