Merge changes Ia764b341,I4e4b41bb,I61b262d8,Ie6ace6bd,I21e866c7, ...

* changes:
  Let tests enumerate all transports/capabilities.
  Destroy networks as soon as they are disconnected.
  Fix a ConcurrentModificationException crash.
  Unify behavior of various cases of "no underlying networks"
  Fix: VPNs update caps upon underlying network disconnect.
  Add tests for setUnderlyingNetworks.
  Fix setCapabilities.
  Fix SSID not being logged by the validation logs
  Make sure getActiveNetwork is consistent with default callbacks
  Add tests for getActiveNetwork.
  Guard the SSID with NETWORK_SETTINGS
  Add a new ssid field in NetworkCapabilities.
  Notif manager and captive portal app to read SSID again
  Remove unwanted capability from the java-doc
  Actually @hide unwanted capability methods.
  API council requested tweaks to NetworkRequest.
  Add OEM_PAID capability to system api
  add airplane mode shell commands to connectivity
  Enable cleartext for captive portal apps
  Expose CONNECTIVITY_ACTION to Instant Apps
  fix isActiveNetworkMetered with VPNs