Add CDM dependency in Tethering

This change introduces a limited library for dependencies on
framework-connectivity from Tethering,
connectivity-internal-api-util, where all classes are annotated with
@RequiresApi(S) to ensure proper API checks are done before usage.

Bug: 245972418

Change-Id: I82bafd9063341adc71d07f0858e6d68283d081f0