Add missing malformed tests for publish packets

Summary:
related to T12015
- all malformed cases should now be fully covered!
- additionally, added a receive channel overflow test

Reviewers: ivica

Reviewed By: ivica

Subscribers: miljen, iljazovic

Differential Revision: https://repo.mireo.local/D27709

include/async_mqtt5/error.hpp

@@ -86,7 +86,7 @@ enum class error : int {
 	subscription_identifier_not_available,
 
 	/** The Server does not support Shared Subscriptions. */
-	shared_subscription_not_available,
+	shared_subscription_not_available
 };
 
 
@@ -122,6 +122,11 @@ inline std::string client_error_to_string(error err) {
 	}
 }
 
+inline std::ostream& operator<<(std::ostream& os, const client::error& err) {
+	os << client_error_to_string(err);
+	return os;
+}
+
 struct client_ec_category : public boost::system::error_category {
 	const char* name() const noexcept override { return "mqtt_client_error"; }
 	std::string message(int ev) const noexcept override {