[clang-tools-extra] Add option to exclude headers from clang-tidy analysis (PR #91400)

[Nick Desaulniers via cfe-commits]

nickdesaulniers wrote:

For the life of me, I cannot figure out how the hell to get `ExcludeHeaderFilterRegex` in a `.clang-tidy` file to work...

Trying to exclude more than one file.  @justincady help!

https://github.com/llvm/llvm-project/pull/91400