Add public ApnSetting in android.telephony.

Bug: 68208293
Test: manual

Add public ApnSetting class in android.telephony. Move APN TYPE constants out from
PhoneConstants into public ApnTypeConstants.

Design doc: https://docs.google.com/document/d/1UEYjhRGSEwwccPLs_FzFD-IeOsVq63gxmAHNtDfnzAY/edit?pli=1#

Change-Id: I74d23644a872df0abc19730285ae196b6e3e39dd
5 files changed