[clang] [clang-tools-extra] [clang-tidy][clang][diagnostics] Unify system header/macro supression (PR #193774)

[Donát Nagy via cfe-commits]

NagyDonat wrote:

@AaronBallman @tbaederr @dbartol I would be very grateful for a review of the NFC changes within `DiagnosticIDs.{cpp,h}`.

These changes can be found in the commit https://github.com/llvm/llvm-project/pull/193774/commits/64898864dcaec3b00f78de4190f268007e703109 -- while the rest of the PR modifies Tidy code.

https://github.com/llvm/llvm-project/pull/193774