message: runtime: add static layer case to loader impl
diff: @@ -474,6 +474,9 @@ LoaderImpl::LoaderImpl(Event::Dispatcher& dispatcher, ThreadLocal::SlotAllocator
  throw EnvoyException(absl::StrCat("Duplicate layer name: ", layer.name()));
  }
  switch (layer.layer_specifier_case()) {
  + case envoy::config::bootstrap::v2::RuntimeLayer::kStaticLayer:
  + // Nothing needs to be done here.
  + break;
  case envoy::config::bootstrap::v2::RuntimeLayer::kAdminLayer:
  if (admin_layer_ != nullptr) {
  throw EnvoyException(
  @@ -494,8 +497,7 @@ LoaderImpl::LoaderImpl(Event::Dispatcher& dispatcher, ThreadLocal::SlotAllocator
  init_manager.add(subscriptions_.back()->init_target_);
  break;
  default:
  - ENVOY_LOG(warn, "Skipping unsupported runtime layer: {}", layer.DebugString());
  - break;
  + NOT_REACHED_GCOVR_EXCL_LINE;
  }
  }
  