Add "Broadcast" button at output switcher

1.Add ”Broadcast“ button at output switcher. like the UX mock P9.
2.If the user launches the the broadcast at first time, then the
UI shows the educational dialog. like the UX mock P8.

Bug: 227109903
Test: manual test
Change-Id: Icc4272b3f37e5ed68280a5a5a5efabb766a683e0