Implement Dumpable on StatusBarStateController

We need a good way of viewing some recent historical state for
StatusBarStateController in order to track down the failure mode for
some tricky bugs

Bug: 126967039
Test: adb shell dumpsys activity service SystemUI | grep
StatusBarStateController -A10 #should have info about StatusBarStateController

Change-Id: Ie5c6eded90c84439d071e51c6c012f15387c10e5