Move tethering out of ConnectivityService. All client would
use TetheringManager to talk with TetheringService directly.
Bug: 144320246
Test: -build, flash, boot
-atest TetheringTests
Change-Id: Ib051bea724a256f9c4572b566e46ae7b9c4abe6e
Merged-In: Ib051bea724a256f9c4572b566e46ae7b9c4abe6e
This is initial patch that don't contain any service for now.
Bug: 136040414
Test: -build, flash, boot
Change-Id: I0b49d7e9c3fcba5af3025163f9cc9eafb0778116