This fixes an issue where building with an old deployment target would
cause apps to display in "unsafe" screen areas.

This change stops menus from displaying under notches/cutouts on mobile
platforms.

This behaviour more closely mirrors the behaviour of other applications.

Previously, a touch on a component outside the Viewport would interrupt
and cancel a scroll gesture inside the Viewport.

Now, the Viewport will respond to all drag events from the input source
that started the drag, allowing the Viewport to be scrolled with one
input source while adjusting other controls with another input source.

The FontsDemo is useful for testing this behaviour, as it has two
Viewports on a single screen, along with some other controls.

Zenity and Kdialog only support opening either files or directories
during a single invocation.

This restores the behaviour of TreeViews with custom item components prior to ec990202

Calling AccessibilityHandler::getChildren() or getParent() may cause an AccessibilityHandler object to be created and an InternalAccessibilityEvent::elementCreated notification to be sent. Calling AndroidAccessibilityEvent.setSource may then cause a recursive populateNodeInfo() call.