Migrating SettingsLib tests to /external/robolectic.

FragmentController was a hack added to Android's /external/robolectric-shadows.
Moving that debt to /framework/base sub repos.
Updating testutils to new robolectric restrictions.
Using the OverpowerReflectionHelpers where required.

(Cherrypicked from ag/23845147)

Bug: 261728063
Test: atest SettingsLibRoboTests
Change-Id: I8e6fcfdd70375a76e94d904adcbb27904938175c