[Mobile] Migrate to qt6.9.2 and remove safe area hacks

[alexjba]

This PR introduced some hacks in order to fix the safe area on Android: #18290

The solution should come from this fix https://bugreports.qt.io/browse/QTBUG-135808 available in 6.10 and 6.9.2.

To verify once the hack is removed:

• Safe area has values when launching the app with no account (initial onboarding)
• The safe area is preserved after rotating the device
• The safe area OS text and icons are visible in the top safe area