This change adds TestAPIs for tests to retrive an instance of ConnectivityManager, allowing it to build test TUN interfaces, as well as test networks. This also integrates the TestNetwork types with ConnectivityManager, creating virtual networks if the network agent is a test agent. Bug: 72950854 Test: Compiles, CTS tests using this passing correctly Change-Id: I741ef9cdf4bd4125d9129af3a030edf32f438e4f