[SysUI] Add Low Quality QS indication

Add Low Quality QS indication to WiFi when it is still connected and
validated but is not the default network (most likely an indication
that it has a low score).

Bug: 163627176
Test: visual (using `adb shell cmd wifi set-connected-score 49` to
simulate a low score)
Test: atest NetworkControllerWifiTest

Change-Id: Ib0d0194b20b8cb824faebea1af5461c553be859e