WifiNetworkFactory: Implement UI activity start

UI activity will be started every time we start processing a new
request.

The corresponding UI implementation is under review in ag/5605669.

Bug: 113878056
Test: ./frameworks/opt/net/wifi/tests/wifitests/runtests.sh
Change-Id: I27af3edb5571a33fb8caa7ffebd50d3b8a7cf580
2 files changed