Log VCN network connected and disconnected events.

Note that disconnected events are also important for getting correct validated duration metrics. Since they are whenever we teardown the network or VcnConnectionConfig, they will mark the end duration for network validated state also.

Flag: EXEMPT METRICS
Test: atest FrameworksVcnTests, CtsVcnTestCases
Bug: 288600040
Change-Id: I34401568287700e6ab356cff029620b6372354d0
2 files changed