Implement phone.confirmCall

[aykutalparslan]

Complete phone call E2E encryption key exchange »

phone.phoneCall#ec82e140 phone_call:PhoneCall users:Vector<User> = phone.PhoneCall; ---functions--- phone.confirmCall#2efe1722 peer:InputPhoneCall g_a:bytes key_fingerprint:long protocol:PhoneCallProtocol = phone.PhoneCall;