Shortcut Helper - Implement lifecycle of new version

- Repository holds the lifecycle state. It listens to system events
  (show, hide, toggle requests) and ui events (user leaving) to map the
  lifecycle state
- ShortcutHelperActivityStarter starts the activity when state becomes
  active
- ShortcutHelperActivity finishes itself when the state becomes inactive

Bug: 335387428
Test: Unit tests in this CL
Test: Manually
Flag: com.android.systemui.keyboard_shortcut_helper_rewrite
Change-Id: Icf4d24440f5bc0937bfee48c859c0d40db979883