LibJS+Everywhere: Convert JS::Error to String

This includes an Error::create overload to create an Error from a UTF-8
StringView. If creating a String from that view fails, the factory will
return an OOM InternalError instead. VM::throw_completion can also make
use of this overload via its perfect forwarding.

Meta/Lagom/Tools/CodeGenerators/LibWeb/BindingsGenerator/IDLGenerators.cpp

@@ -1216,7 +1216,7 @@ static void generate_to_cpp(SourceGenerator& generator, ParameterType& parameter
             // 19. Throw a TypeError.
             // FIXME: Replace the error message with something more descriptive.
             union_generator.append(R"~~~(
-        return vm.throw_completion<JS::TypeError>("No union types matched");
+        return vm.throw_completion<JS::TypeError>("No union types matched"sv);
 )~~~");
         }