Add Open button to launch instant app.

- move logic from InstantAppButtonsController into
InstantAppButtonsPreferenceController, as it is not really necessary to
have separate control to be in different class.
- add logic to check if the instant app provides a default launch uri.
If so, show a Open button to launch the uri, and move the Install
button into option menu. If not, Install button remains as is.
- also update the instant app button layout to match the regular 2
buttons layout.

Change-Id: Ibcae780ad697ca93a48604b03c8f4600dd3c0472
Fixes: 69562807
Test: make RunSettingsRoboTests