[llvm] [WebAssembly] Implement lowering calls through funcref to call_ref when available (PR #162227)

[Derek Schuff via llvm-commits]

https://github.com/dschuff commented:

Since you are adding a new instruction I think we also need MC tests that cover assembling them, (like the tests in test/llvm/MC/WebAssembly) so we can cover things like encodings of instructions (and e.g. check out the tests that cover use of __indirect_function table).

https://github.com/llvm/llvm-project/pull/162227