DisplayCutout: Reload displays when resource overlays change

This allows the DisplayManager to pick up changes to the
DisplayCutout resource, which is used to implement emulation
of the overlay.

Bug: x
Test: adb shell overlay enable ...; verify cutout is picked up immediately and not only after toggling the display
Change-Id: I0fa2d50366a17231f45990d2d3854321d48653f0