Android apps do not fill screen with MaximizeUsingFullscreenGeometryHint

Related to QTBUG-64574,

flags: Qt.MaximizeUsingFullscreenGeometryHint

does not fill the entire display. Reading the docs it seems that it should also hide the nav bar, this doesn't seem to do that, but it works as described on iOS.

In the activity's onCreate() this needs to happen Java code:

View decorView = window.getDecorView();
		int uiOptions = decorView.getSystemUiVisibility();
		uiOptions |= View.SYSTEM_UI_FLAG_HIDE_NAVIGATION | View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY;
		decorView.setSystemUiVisibility(uiOptions);