Replace ConnectivityManager as TetheringManager

Tethering APIs are all move to TetheringManager from Android R.
1. Replace ConnectivityManager tethering API usage as TetheringManager.
2. Use TetheringManager#stopTethering to disable usb tethering instead
of using deprecated ConnectivityService#setUsbTethering
3. Use TetheringManager#stopTethering to disable bluetooth tethering
instead of directly use BluetoothPan#setBlueoothTethering. So bluetooth
getProfileProxy is not needed in TetherService because tethering would
do that when calling #stopTethering.
4. Also support TETHERING_ETHERNET entitlement check that
TETHERING_ETHERNET is new added from Android R.

Bug: 146918263
Test: atest TetherServiceTest
Change-Id: Id969f29d7210f2ee32719c76439049bbc86cd4f6
Merged-In: Id969f29d7210f2ee32719c76439049bbc86cd4f6