Reduces the code a compiler including qsignalspy.h needs to parse and codegen. The order of the functions in the .cpp file is chosen to minimize the diffs to follow-up changes. We can't de-inline the private ctor, because that would pin the vtable to the qsignalspy.cpp TU, which would require us to export the class wholesale to make the vtable accessible to users of the class, but we can't export the class because it inherits QList. Task-number: QTBUG-123544 Change-Id: Ib26fdb68e1fc0e6f6919e4cd25759b7047f9977c Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>