clang-tidy: issues in PublisherSubscriberTest.cpp

[debruce]

1. case style: num_publish_messages (line 21), ValidateMessages (line 69)
2. do not use namespace using-directives; use using-declarations instead at line 23
3. use override for destructor at lines 41
4. magic numbers: line 52
5. not initialized: rx_queue_mtx (line 94), message (line 108), rx_queue_mtx, (line 129), rx_queue_mtx2 (line 140), message (line 153), rx_queue_mtx (line 174), message (line 194), rx_queue_mtx (line 217), message (line 241), message2 (line 248)
6. bogus if-then-else error buried in a gtest macro: line 103, 137, 148, 183, 189, 225, 236
7. unused: message (line 186)
8. TestBody with cognitive complexity issues at line 208