Android: Fix floating dockers becoming unresponsive

In Qt's internal compositor API for Android, it added windows to windowStack based on when they were created. For the most part this worked. However in some cases Dock widget were created before the parent widget. This resulted in all events going to MainWindow, even when dock widget was used.

The cases where this happened: app was in pause and the SurfaceView was totally torn down (rendered black). App is restarted with Dockers floating.

Note:

Two APIs aren't implemented for m_popupStack:

void raise(QAndroidPlatformWindow *window);
void lower(QAndroidPlatformWindow *window);

They aren't hard to implement but hard to test.

Test Plan

Primary test:

Have some dockers floating, close Krita. Reopen it, the dockers should now be responsive.

Because getting all combinations of windowTypes is hard, this patch has to be tested passively.

Formalities Checklist

• I confirmed this builds.
• I confirmed Krita ran and the relevant functions work.
• I tested the relevant unit tests and can confirm they are not broken. (If not possible, don't hesitate to ask for help!)
• I made sure my commits build individually and have good descriptions as per KDE guidelines.
• I made sure my code conforms to the standards set in the HACKING file.
• I can confirm the code is licensed and attributed appropriately, and that unattributed code is mine, as per KDE Licensing Policy.