[clang-tools-extra] [clang-tidy] Add new check `llvm-prefer-static-over-anonymous-namespace` (PR #142839)

[Baranov Victor via cfe-commits]

vbvictor wrote:

> I suppose this patch does not impede further refactoring if we want to go in that direction in the future.

Yes, also with these tests we will be sure that future `llvm-` alias works properly.

https://github.com/llvm/llvm-project/pull/142839