Refactor WifiScanWorker

Extracted WifiScanWorker from WifiSlice

Bug: 128056349
Test: make RunSettingsRoboTests -j ROBOTEST_FILTER=com.android.settings.wifi
Test: make RunSettingsRoboTests -j ROBOTEST_FILTER=com.android.settings.slices
Change-Id: I9b3c809ee6c2b7466c959631840b257b91b49d88
5 files changed