[Provider model] Internet picker Part II

 - Add mobile internet preference with default data subscription.
 - Make prefrence to show dynamically when data subscription changed.

Video exhibition
 - http://rcll/gcmsphfhJ1UzfPSvjWOuXK/c1B2CtaFz27rlIQ2LSTJmo

Code difference
 - SubscriptionsPreferenceControllerTest.java between robolectric and junit.
  - https://diff.googleplex.com/#key=1Zm7JGPhoZwY

Bug: 172229552
Test: atest SubscriptionsPreferenceControllerTest

Change-Id: Ib50c2c51159f60f19631d1a02081eafde3436e94