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

[Rahul Joshi via llvm-commits]

jurahul wrote:

I guess the process is similar to how we add decoder namespaces today, just expressed differently so that we end up with a single decoder table. For "hard" conflicts, we will get an error message unless we have the resolve-conflicts-try-all enabled. For "soft" conflicts, we today do not get any error message today and I guess folks need to debug (so no changes there).

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