Revert "Telephony: Incoming Call in Background (2/3)"

This reverts commit 1c50d3a5613b39af72bdcf63f2fae65eb9c3ab66.
Revert "Revert "[2/3] Telephony: allow disabling non intrusive incall ui""

This reverts commit 63e7eeae934669c41263a385d18d2e19a548fdcc.