(Un)subscribe validates the number of topics and reason codes

Test Plan:
related to T12015
- (un)subscribe reason codes will always contain as many reason codes as there are topic filters
- if, by some odd chance, the client receives the wrong number of rcs or some are invalid, it will treat it as malformed
- both subscribe_op and unsubscribe_op should be 100% covered by tests now

Reviewers: ivica

Reviewed By: ivica

Subscribers: miljen, iljazovic

Differential Revision: https://repo.mireo.local/D27592

test/include/test_common/packet_util.hpp

@@ -361,6 +361,11 @@ std::vector<std::string> to_readable_packets(const ConstBufferSequence& buffers)
 	return content;
 }
 
+inline disconnect_props dprops_with_reason_string(const std::string& reason_string) {
+	disconnect_props dprops;
+	dprops[prop::reason_string] = reason_string;
+	return dprops;
+}
 
 } // end namespace async_mqtt5::test