Fix PiP disappearance after unlock

KeyguardUpdateMonitor uses WeakReference internally for all the
registered callbacks, therefore an anonymous class may be released and
unable to receive any callback after registration.

Changed also the ConfigurationListener and
KeyguardStateController.Callback in WMShell.

Bug: 241249835
Test: repeatedly lock and unlock device with PiP being present
Change-Id: I1c3ea269ee9955847212bebbebdd0d7130dbdce5