[llvm] [WebAssembly] Add RefTypeMem2Local pass (PR #81965)

[Paulo Matos via llvm-commits]

pmatos wrote:

> @pmatos Yes, replacing the mem2reg with this pass seems to work on all existing LLVM and Emscripten reference type tests. I am planning to upload the that, I mean the replacing, as a follow-up to this PR.

Excellent. LGTM. It turned out simpler than what I had imagined. Nice patch. 

https://github.com/llvm/llvm-project/pull/81965