Migrates residual Lts sources to generated rtiddsgen API

Adds NmeaManagement tests, fixes codegen includes and Qt6 SerialPort CMake target.

qt6-after/qt6-migrated-legatus/Lts/Proxies/TrainingAreaBase/dds_handler.cpp

@@ -60,7 +60,7 @@ bool DdsHandler::init(const QStringList &qosFileList)
   assert(m_dtcPartitionTime.get());
   m_dtcPartitionTime->setSubscriberCallback([this](const Core::PartitionTime & data, DataModification)
   {
-    m_curMSecSinceEpoch = data.timeStamp();
+    m_curMSecSinceEpoch = data.timeStamp;
   });
 
   // default dts:...