[clang] [Clang][WebAssembly] Fix WASM tables to allow `__funcref` function pointers (PR #178720)

[Paulo Matos via cfe-commits]

pmatos wrote:

> Okay! Good to know.
> 
> In that case, @pmatos, please give it one more look over and merge it in if everything's good.

LGTM but I cannot land it. Lost my commit priv last month during a cleanup. 
@dschuff ?

https://github.com/llvm/llvm-project/pull/178720