[clang-tools-extra] [clang-tidy][NFC] Remove regex hacks to match full lines in tests (PR #162293)

[Nicolas van Kempen via cfe-commits]

https://github.com/nicovank approved this pull request.

Thanks! LGTM, some cosmetic whitespace comments. Only minor concern is `readability/function-cognitive-complexity.cpp`.

https://github.com/llvm/llvm-project/pull/162293