[clang] [CIR] Add the ability to detect if SwitchOp covers all the cases (PR #171246)

[Henrich Lauko via cfe-commits]

xlauko wrote:

@badumbatish please apply requested changes completely next time, the desctription did not match the actual format.
We use snake_case for attributes and MLIR assembly form. I fixed it here https://github.com/llvm/llvm-project/pull/172153

https://github.com/llvm/llvm-project/pull/171246