Overlay, actor, and target app visibility handling

Hooks AppsFilter to support exposing a target and any overlays
targeting it to the actor specified in its overlayable block.

Sacrifices some install-time performance in favor of less memory
usage and easier to follow code by doing a full search/rebuild
on each change.

Benchmarks TBD

Bug: 143096091

Test: atest OverlayReferenceMapperTests

Change-Id: Ic832818b9aa383f1167ca3e69a11b8459fa9db97