UpstreamNetworkMonitor: add NOTIFY_TEST_NETWORK_AVAILABLE

Used for test interface upstream can replace existing non-test
upstream interface, like ethernet on cuttlefish.

This helps to fix the flaky test when we are using test interface on
cuttlefish. Because the ethernet and test interface upstream update
event order can't be guaranteed.

Bug: 237369591
Bug: 242067530

Test: atest ConnectivityCoverageTests
Change-Id: I9da71ee116bf1ebc9831f61f25acf42e328a8370
4 files changed