API Review PhoneManager -> TelecommManager. Rename methods (3/6)

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: I8285f15747b66fdfad93d203d848d4a62c0f9b2a