[llvm] [TableGen][DecoderEmitter] Add option to emit type-specialized `decodeToMCInst` (PR #146593)

[Rahul Joshi via llvm-commits]

jurahul wrote:

Actually, `git grep CppTypeName` shows a lot of hits in LLVM, so there is precedent on LLVM side as well.

https://github.com/llvm/llvm-project/pull/146593