Add Nullable/NonNull Annotations where appropriate.

Bug: 126701249
Bug: 126701136
Bug: 126701236
Bug: 126700627
Bug: 126702224
Test: atest FrameworksTelephonyTests
Merged-In: I4cfba9dee766fa9d34f578db4143919c3f203a20
Change-Id: I4cfba9dee766fa9d34f578db4143919c3f203a20
5 files changed