[llvm] [TableGen] Add InstrInfoEmitter options for operand type/size mappings (PR #125797)

[Rahul Joshi via llvm-commits]

jurahul wrote:

> What's the measured impact of this change?

I don't have one. In a downstream backend I am working on though, I did notice that these type mappings generate quite a bit of code that is unused. For operand size mappings, its specific to X86 as it looks for X86MemOperand. So, we could potentially remove the option and just bail out if `getInstNamespace() != X86`, but that seemed less kosher than adding an option.

https://github.com/llvm/llvm-project/pull/125797