1/n refactoring ViewModels for touchpad tutorial

Extracting handling of easter egg to separate ViewModel to not repeat it in all gesture view models

1. Simplifying TouchpadGestureHandler so that it accepts any gesture recognizers and is not directly dependent on easter egg monitor
2. EasterEggMonitor now extends GestureRecognizer
3. Easter egg handling logic is extracted to separate ViewModel

Bug: 384509663
Test: EasterEggGestureViewModelTest
Flag: com.android.systemui.shared.new_touchpad_gestures_tutorial
Change-Id: I46dd032a992f27252dd95510b77ccaf30f78096d