Android a11y: Changes to Accessible.ignored and Item.visible are not propagated to the screen reader

See the attached MWE. The screen reader registers only changes to visible == false. The states visible == true, ignored == false and ignored == true are only updated when other events trigger an update of the parent.

There are two causes for this behavior:
1. QAccessible::ObjectShow events are not considered in QAndroidPlatformAccessibility and the whole chain up to QtAccessibilityDelegate.java
2. QQuickAccessibleAttached does not send QAccessibleEvents for updates of the "ignored" property