[clang-tools-extra] [clang-tidy][NFC] Enable "HeaderFilterRegex" in clang-tidy codebase (PR #167020)

[Victor Chernyakin via cfe-commits]

================
@@ -1,4 +1,6 @@
 InheritParentConfig: true
+HeaderFilterRegex: 'clang-tools-extra/clang-tidy'
+ExcludeHeaderFilterRegex: 'include-cleaner|clang-query'
----------------
localspook wrote:

I think this is the relevant code:
https://github.com/llvm/llvm-project/blob/77342761a9060159f09c0c6d5aa3da2e543a4877/clang-tools-extra/clang-tidy/ClangTidyDiagnosticConsumer.cpp#L590-L594
Maybe we should normalize `FileName` before matching on it? i.e.:
```txt
clang-tools-extra/clang-tidy/misc/../../include-cleaner/include/clang-include-cleaner/Types.h
->
clang-tools-extra/include-cleaner/include/clang-include-cleaner/Types.h
```

https://github.com/llvm/llvm-project/pull/167020