Add API surface for ConnectivityDiagnostics API.

ConnectivityDiagnostics API will be used to provide callbacks to
permissioned applications for notifications on network connectivity
events.

Bug: 143187964
Test: compiles
Change-Id: Ib3c0b93f534a9c540e577891aa8aa0a2ad6de71f
1 file changed
tree: a9f9f634f351d3f0fbbed4d955ba51bb554869b4
  1. core/
  2. services/
  3. tests/