[DO NOT MERGE] Support multiple smartspace views

Previously, a singleton view was reused in multiple places. However,
this does not work when multiple displays are in use, such as when
casting the device display to another screen. Supports sets of views
that are activated when they are attached to windows, and removed when
they are detached.

Fixes: 196175396
Test: atest LockscreenSmartspaceControllerTest
Change-Id: Ied1ecff9103d8539f075785409d2951a1be21ab2