API review PhoneManager -> TelecommManager. Rename methods (6/6)

PhoneManager
- handlePinMMI docs should explain what a Pin is and what MMI is
- rename isInAPhoneCall to isInCall
- rename showCallScreen to showInCallScreen
- merge this class into TelecommManager, we don't need both

Bug: 16960458

Change-Id: I7d573e27ed093f2ddb7849703cc62f9916835393