[clang-tools-extra] [clang] [clang-tidy] fix misc-const-correctnes false-positive for fold expressions (PR #78320)

[Piotr Zegar via cfe-commits]

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

LGTM, but i'm not 100% sure about ExprMutationAnalyzer part (if thats a right place).
Leave it open for few days, so others could comment if they have objections.

https://github.com/llvm/llvm-project/pull/78320