Restore qRegisterMetaType for Q_ENUMed enums

It's odd - because one reason to swap to Q_ENUM is to gain
automatic registration of these types, so it should work
without the manual registration. Might be a SIP binding issue...

src/core/qgsapplication.cpp

@@ -146,7 +146,9 @@ void QgsApplication::init( QString profileFolder )
   qRegisterMetaType<QgsGeometry::Error>( "QgsGeometry::Error" );
   qRegisterMetaType<QgsProcessingFeatureSourceDefinition>( "QgsProcessingFeatureSourceDefinition" );
   qRegisterMetaType<QgsProcessingOutputLayerDefinition>( "QgsProcessingOutputLayerDefinition" );
+  qRegisterMetaType<QgsUnitTypes::LayoutUnit>( "QgsUnitTypes::LayoutUnit" );
   qRegisterMetaType<QgsFeatureIds>( "QgsFeatureIds" );
+  qRegisterMetaType<QgsMessageLog::MessageLevel>( "QgsMessageLog::MessageLevel" );
 
   QString prefixPath( getenv( "QGIS_PREFIX_PATH" ) ? getenv( "QGIS_PREFIX_PATH" ) : applicationDirPath() );
   // QgsDebugMsg( QString( "prefixPath(): %1" ).arg( prefixPath ) );