Add basic IpReachabilityMonitor integration test.

    - verify the specific number of unicast NS for probe.
    - verify the notifyLost() callback will be triggered if probe
      failed.
    - verify the notifyLost() callback won't be triggered if
      probe succeed(i.e. receive solicited NA as reply).

Bug: 162944199
Test: atest NetworkStackIntegrationTest NetworkStackTests
Change-Id: I6ea04a624b0f0485625a3ec46d7a5544f9d2713b