Implement subtype checking for [return_]call_indirect
instructions
#9448
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When Wasm GC is enabled, the
[return_]call_indirect
instructions must do full subtyping checks, rather than simple strict equality type checks.This adds an additional branch and slow path to indirect calls, so we only emit code for this check when Wasm GC is enabled, even though it would otherwise be correct to always emit it (because the
is_subtype
check would always fail for non-equal types, since there is no subtyping before Wasm GC).