[clang] [Clang] Diagnose fixed point arithmetic with `_BitInt` and `overflow` behavior types (PR #221134)

[Shafik Yaghmour via cfe-commits]

shafik wrote:

There was a duplicate issue: https://github.com/llvm/llvm-project/issues/196948

and a fix was landed for that that already fixed this issue: https://github.com/llvm/llvm-project/pull/199912

https://github.com/llvm/llvm-project/pull/221134