Replace ConnectivityManager hidden symbols on Telephony

Connectivity is becoming a mainline module in S, so
ConnectivityManager hidden symbols can not be used for outside
components. Besides, most Tethering relevant methods or variables
on CM are migrated to TetheringManager. So replace all these
methods or variables from ConnectivityManager to TetheringManager
on Telephony.

Bug: 180693313
Test: atest FrameworksTelephonyTests:DeviceStateMonitorTest
Change-Id: I0a7dccbea1295cbb665106ee9a2a8705ee2c7ba7