[Testing] Use AndroidJUnit4 instead in MobilePlanPreferenceControllerTest

1. Use AndroidJunit4 instead of RobolectricTestRunner
2. Add @Before setup() for context
3. Change Copy Right
4. Workaround the resource getString to resolve the resource not found

Bug: 167997296
Test: atest -c MobilePlanPreferenceControllerTest
Change-Id: I5f43b6a4d20108195164038c02810b725abbcd06
1 file changed