[Status Bar] Move icon controller's CommandQueue.Callbacks into object.

Bug: 265307726
Test: atest StatusBarIconControllerImplTest
Test: manual: (1) Be in silent mode. (2) Make a phone call. (3) Mute the
phone call. -> Verify that *both* silent *and* mute icons appear in the
status bar. Verify that they can each be toggled independently without
affecting each other.

Change-Id: Id3c9a0883412c41943932f8fc887d36690ea8ee0