Introduce ANSWER_PHONE_CALLS permission

See I4c33fcea6b95a30469fa6c0c37090be32b0ad52e

Test: Grant the permission and ensure the call gets answered.
Deny the permission, and ensure that the API call throws an exception.
Bug: 30932767
Change-Id: Idc214408e57e15224b1874b08d80b747ebf95f3b
2 files changed