Register notification panel key gesture handler in SysUi

Reasons to move away from the existing PhoneWindowManager pipeline:
1. the existing pipeline has too many redirection. It is less performant compared to the KeyGestureHandler approach.
2. the existing pipeline does not expose the focus display ID from the Input framework. However, the KeyGestureEvent does contain this ID. While we don't intend to use the Input framework's focus display ID at this time, it's beneficial to retain access to it for potential future use.

Test: atest WmTests:PhoneWindowManagerTests
Test: atest SystemUITests:SysUIKeyGestureEventInitializerTest
Flag: com.android.window.flags.enable_key_gesture_handler_for_sysui
Bug: 406740557
Change-Id: I7ba732d65633696fb3abbc6ad8dddb74a41ee228