Implementing TutorialSelectionScreen

TutorialSelectionScreen is first screen appearing when coming from settings and lets user choose which tutorial to do.
This is just a rough implementation, there's not visd yet but it's a good starting point.

Also making the whole activity properly full screen

Flag: com.android.systemui.new_touchpad_gestures_tutorial
Fixes: 346580488
Test: manually, launch activity with intent: adb shell am start -a com.android.systemui.action.TOUCHPAD_TUTORIAL -c android.intent.category.DEFAULT
Change-Id: Iaa3d3e2925eb6f60456718e840621c988c5f94fc