Cut the dependency to APN constants

With Telephony moving to Mainline these constants are not accessible
any more, and should not be made public. As they are only used by
a deprecated method that can only be called by apps with a target
SDK < M and only for one of the features it used to handle, copying
the constants until this method is completely removed is the simplest
way to go.

Test: FrameworksNetTests
Bug: 144454341
Change-Id: Iea18c8d2f2c8a40f04db9383d3f74b917267ba25