Merge PanelEventsEmitter into ShadeExpansionStateManager

The purpose is to further consolidate and standardize how changes
in the shade state are propogated throughout the system. The change
renames NotifPanelEvents, merges the PanelEventsEmmitter impl into
ShadeExpansionStateManager, and deletes the FakeNotifPanelEvents impl,
which is unnecessary given the simplicity of ShadeExpansionStateManager.

Bug: 254512692
Test: atest and manual verification
Change-Id: I4d3e580eb2e8838b84b32fd1f1cdb05098db49ff