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

[Baranov Victor via cfe-commits]

vbvictor wrote:

> but I'll understand if people think this is too big and ask for it to be split up (in which case: how many chunks would you like?).

Personally, I can review right-away mechanical test change with 500-600 lines or 150-200 NFC refactoring change.
But since we rarely have big refactor changes, I'm fine doing it in one go.

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