[SB Refactor] Only show wifi icon if (1) the network is active and

validated; or (2) we're configured to always show it when enabled.

This matches part of the logic in
WifiSignalController#notifyListenersForNonCarrierWifi.wifiVisible.

Test: manual: With alwaysShow config off, verify that the wifi icon only
appears when we're fully connected to a network
Test: manual: With alwaysShow config on, verify that the wifi icon
always appears (unless wifi is disabled)
Test: statusbar.pipeline tests
Bug: 238425913

Change-Id: I723cfc0435265699f98b5b1adeb4cb9bbfaf2929