Revert "LayerActivity: Corrected lifecycle"

This reverts commit 7aaea48c77670f048808a16324ba00a102a810cf.
Revert "HALO: Option to pause the underlying app (1/2)"

This reverts commit 26c323f0e4bff7f69c235c19d3c75d716265982a.
Revert "HALO cleanup"

This reverts commit d80410ab45e8f5e0c7b48a162eb53d1dbd500668.