Adding action key tutorial that uses Alt key

We don't have access to Action/Meta key yet so for now let's just listen to LeftAlt key and pretend it's action key.
Extra changes:
- extracting ActionTutorialContent from GestureTutorialContent - by "action" I mean gesture/pressing key or whatever else tutorial is about
- substituting GestureState by ActionTutorialState in generic parts of UI

Bug: 354915537
Test: open action key tutorial, automated tests to come when we have real key pressing logic
Flag: com.android.systemui.shared.new_touchpad_gestures_tutorial
Change-Id: Ie049afbf2d17256b7beab6f887d085bebc34f8d1