Add new power button behavior that asks keyguard to show the hub

This behavior is an extension of the existing
SHORT_PRESS_POWER_DREAM_OR_SLEEP behavior that attempts to trigger the
glanceable hub (widgets on lock screen) if available first, before
attempting to trigger the dream or just going to sleep.

This is a SysUI feature that shows on top of keyguard so we ask
keyguard to show it along with locking the device.

Bug: 378170118
Test: atest KeyguardViewMediatorTestKt DreamManagerServiceTest PhoneWindowManagerTests
      also manually verified on device
Flag: com.android.systemui.glanceable_hub_v2
Change-Id: I8ec299db21926abdb3d282199fb5e6ba102b2345