Implement headless PreCall

If no actions require an activity, instead of launching the PreCallActivity, all actions will be performed immediately, and the call intent will be sent to telecom directly.

This reduces the latency & risk when mutli SIM is not supported.

Bug: 68953196
Test: PreCallImplTest, HeadlessPreCallCoordinatorTest
PiperOrigin-RevId: 176032790
Change-Id: I03258e8643f18c65a8e5b1a84b18b71b30638044
6 files changed