Wait for KeyguardService#onScreenTurningOn when switching displays

Updates DeferredDisplayUpdater to wait for the keyguard
to send an 'onDrawn' callback before marking the display
switch Shell transition as ready.

Keyguard will add SHOW_WALLPAPER flag in the onScreenTurningOn(onDrawn)
 callback, waiting for the onDrawn callback will ensure that
 the wallpaper is part of the transition.

Bug: 395612286
Flag: com.android.window.flags.ensure_wallpaper_drawn_on_display_switch
Test: atest DisplayContentDeferredUpdateTests
Test: fold/unfold a foldable device
Change-Id: I204a731b41a2693e2c1de5f92eb93bce8ee7e7c6