Verify Qt 6 SCXML module's interoperability with Qt Creator's SCXML editor

Qt Create has a SCXML editor that allows visual editing of SCXML state machines.
This task's purpose is to ensure that Qt 6 SCXML module does not degrade this
functionality.

Qt 6 SCXML module is mostly *) source compatible with Qt 5 SCXML module, and therefore it is assumed that the interoperability exists. However better safe than sorry => best to verify and file Jira items of findings as necessary.

*) senderObject of Q_PROPERTY in qsignaltransition is now symmetrically "const", which could potentially cause some changes