Memory leak while performing pan operations with Map and MapQuickItem.

Attached project shows the behaviour.

How to reproduce:

1. Compile and launch
2. Start pan operation on map with user gesture, and drag map around while performing pan, so some of MapQuickItem will be destroyed and re-created.
   Check gesture.png for sample mouse gesture trajectory: start pan at Star point, and follow the line.
3. When MapQuickItems are outside of visibleRegion, they are destroyed. And recreated when they are inside area.
4. Note significant memory leak.

Note the "timerPan" which is disabled by default. There is no memory leak when pan is performed programmically, i.e. when timerPan is enabled.

This memory leak may be connected with QTBUG-61754