Add a unit-test for TelephonyProvider

This commit adds a unit-test for TelephonyProvider.

TelephonyProviderTestable extends TelephonyProvider but uses an
in-memory database for testing.

TelephonyProvider is also modified to include overridden functions for
testing.

Merged-In: I357f8dde0ec666bdf69457d79c175bcf7b9fc9c6

Test: runtest --path tests/src/com/android/providers/telephony
Change-Id: I357f8dde0ec666bdf69457d79c175bcf7b9fc9c6
Bug: 32073580
3 files changed