Stop sending the new outgoing call broadcast in a blocking manner.

Also remove foreground priority from receivers as well as remove the
ability to launch activities from the background.

Test: Manual testing with flag overridden on and off.
Test: Added unit test to confirm operation with/without the flag set.
Bug: 224550864
Change-Id: I206a822d1a13c68224fd571e3c2bca4b3e7fec0e