AbstractApplication*: Fix reparenting of drawers, Clean up bindings

Querying T.Overlay.overlay attached property on a Binding object was
clearly wrong. It just resulted in null at all times, so basically
those Bindings never took effect.

Since `when:` condition does not make much sense (first, those
properties could never be undefined; second, why reparenting only when
visible?), let's demote them into a property change handlers with null
guards.

For other bindings, pointless `when` check was removed as well as
deprecated (and yet again pointless) restoreMode.

BUG: 473214


Co-Authored-By: Jack Hill <jackhill3103@gmail.com>