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

[rylev]

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.