[clang] [llvm] [clang][NFC] fold ExpressionTraits and TypeTraits helpers into BuiltinTraits.h (PR #210838)

[Matthias Wippich via cfe-commits]

Tsche wrote:

There was a tiny formatting issue (Builtins.h before BuiltinTraits.h rather than after), seems like I undid too much of the autoformatting (it touched other unrelated lines again..). Fixed now.

https://github.com/llvm/llvm-project/pull/210838