Expose time / time zone system apis for telephony

Expose system apis / permissions needed by the telephony module to
communicate with the system server for time and time zone detection.

There are also small improvements for @Nullable.

Bug: 147012511
Test: build only
Merged-In: I27e5aa4c594d5fbad0b6f043afb9e910dcba4349
Change-Id: I27e5aa4c594d5fbad0b6f043afb9e910dcba4349
(cherry picked from commit 2be7ac45)