Add handleCallIntent method in TelecomManager.

This is an @hide method usable only from within Telecom itself in order to
trampoline an ACTION_CALL intent from the UserCallActivity to
Telecom's system service.

Bug: 116719392
Test: Verify that calls initiated via CALL intent no longer get rebroadcast
and are instead sent directly to Telecom.

Change-Id: Ie765631bef8329a8ed12723d9c037a44b4f80882