Show and hide smartspace (2/3)

Remove sending messages to SysUI to hide smartspace.

Instead of setting from WPPG, we organically listen to the
onCurrentClockChanged() to update the smartspace visibility.

Test: tested that the smartspace shows correctly for the preview
Bug: 274927017
Change-Id: I70c324500c6fb65440a1ee3f6676db89d7a298f4