[llvm] [DecoderEmitter] Support for DecodeOrder and `resolve-conflicts-try-all` (PR #157948)

[Rahul Joshi via llvm-commits]

jurahul wrote:

I also want to prioritize the downstream issue with too many namespaces becoming unmanageable and address that first. So I am thinking this:

Change decode ops to not return when decoding succeed but status is fail when the stack is non-empty, but instead continue. This allows to encode attempting multiple decodings without prematurely returning without attempting all. Next, add the resolve-conflicts-try-all which helps our downstream example. Next, drop fallback and fake16 namespaces for aarch64/amdgpu. And then go from there.

https://github.com/llvm/llvm-project/pull/157948