Allow share/edit screenshot actions from lockscreen

- Dismiss keyguard when routing the actions through the proxy receiver
- Fix issue with edit activity also disallowing auto-enter PiP
- Minor cleanup of some unused/shared code

Bug: 72459081
Test: Launch share/edit screenshot from lockscreen (and normally)
Test: Launch screenshot share action with auto-enter PiP activity and
      ensure it does not trigger PiP

Change-Id: Ibae2de51bc3fe10f439d7506ab7d0d9243142c94