[clang] [llvm] [WebAssembly] Refactor Wasm Reference Types as TargetExtType (PR #93428)

[Paulo Matos via cfe-commits]

pmatos wrote:

> This is a re-application of #71540, with the hopes I can get some help from @pmatos and others to finish it. Right now the '../clang/test/CodeGen/WebAssembly/wasm-funcref.c' test fails with an assertion trying to cast the target("wasm.funcref") instruction to a pointer. Looking in to that further but wanted to checkpoint the code here from the first patch.

I will keep this bug in mind but I am taking a leave at the moment until June 3rd. I will take a look at it then.

https://github.com/llvm/llvm-project/pull/93428