Merge changes I3711b362,I49421183,Icc0701cb,I2f5ccc1d

* changes:
  Increase test coverage for VPN info sent to NetworkStatsService.
  Simplify MockVpn.
  Test a VPN with an underlying network that does not yet exist.
  Minor fixes to NetworkCapabilities#toString.
tree: 90cf4ecf5a937a89d59b275d8e6955298054f45b
  1. core/
  2. services/
  3. tests/