Expose PreciseDataConnectionstate#getApnSetting()

Expose an API that was accidentally left as package private.

This is was missed when exposing other methods for the same
class; however, other methods have been deprecated based on
the presumption that this method is available in the public
API.

This method deprecated:
PreciseDataConnectionState#getDataConnectionApnTypeBitMask()
PreciseDataConnectionState#getDataConnectionApn()

Bug: 148565164
Bug: 147600208
Test: make update-api && make offline-sdk-docs
Merged-In: I0207c18d853d0b83db2622ff3abcda98565eac30
Change-Id: I0207c18d853d0b83db2622ff3abcda98565eac30
(cherry picked from commit a61992b6)