Add WIFI_ENABLED and WIFI_DISABLED to StaEvent

Log whenever wifi is turned on/off in StaEvent metrics.

Bug: 112193991
Test: frameworks/opt/net/wifi/tests/wifitests/runtests.sh
Test: Turn wifi on/off from settings
Test: adb shell dumpsys wifi | grep -A10 StaEventList
Change-Id: Icf32d4a622f4447e8461560b7cfa4818dcfb1efa