Add underlying networks into NetworkAgentInfo if any

Now, VPN will set underlying networks into NetworkCapabilities
directly. So the declaredUnderlyingNetworks can also be set
directly when creating a NetworkAgentInfo.

Bug: 191918368
Test: atest FrameworksNetTests:ConnectivityServiceTest
Change-Id: I507072d00ae1eb0c391e5261ab93e359b9c4cb5c
4 files changed