Add ability to require scroll to GlifLayout

Generalize RequireScrollHelper and turn it into a mixin to allow
GlifLayout to use require scrolling.
This is only applicable to GLIF with sticky footer, since inline
content button requires scrolling by definition.

Also added Robolectric test support for full-support, by moving
full-support/test's contents into full-support/test/instrumentation
and put the new Robolectric tests in full-support/test/robotest.

Bug: 36387078
Test: ./gradlew connectedAndroidTest test
Change-Id: Ib07ec0ddf07affa30c46e786f4e9be7853a243c4