[clang-tools-extra] [clang-tidy] Add llvm-regex check (PR #207407)

[via cfe-commits]

furtib wrote:

Hello!
I believe I have responded to all reviews:
- Eliminated duplication with anyOf
- Added char arrays to the checked types
- Replaced if with assert in the logic function
- Rebased from main and converted all documentation to the Markdown format

https://github.com/llvm/llvm-project/pull/207407