[llvm] [LLVM][MC] Introduce `OrFail` variants of MCD ops (PR #138614)

[Rahul Joshi via llvm-commits]

jurahul wrote:

I also found another minor improvement here: Most targets don't generate TryDecode (only AArch64 seems to be generating it), so we could not emit the TryDecode cases for other targets (by tracking whether any TryDecode ops are generated) and eliminate some dead code.

https://github.com/llvm/llvm-project/pull/138614