Deprecated IP connectivity metrics system api

- In order to easily maintain the connectivity service.
Refactor the connectivity service by removing all legacy
metrics code & API.
- The commit will deprecate legacy metrics system api.
(The legacy metrics code will be removed in a separate commit.)
Therefore, those legacy metrics event may not be sent in
Android S and above.

Bug: 177043087
Test: atest ConnectivityServiceTest
      atest IpConnectivityMetricsTest
      atest ConnectivityServiceIntegrationTest
Change-Id: Ia057776869a7d38041b6eaf17904f6c54a7b4fca