[clang] [clang] Warn when builtin names are used outside of invocations (PR #96097)

[Vlad Serebrennikov via cfe-commits]

Endilll wrote:

To clear potential confusion, Corentin suggested to me offline to take over this PR. I fixed the tests and implemented the workaround for `__has_builtin` case, which surfaced while I was fixing the tests.

https://github.com/llvm/llvm-project/pull/96097