`wasmparser::validator::ComponentState::validate_and_register_named_types` should return `Result` instead of `bool`

Right now the validator uses `wasmparser::validator::ComponentState::validate_and_register_named_types` to ensure that a given extern only refers to named types, but it only returns a `bool` instead of a `Result`. This makes debugging much more difficult as one cannot be sure what the actual issue is without using a debugger or patching in a local copy of `wasmparser` to add debug logs.