IMS RAT Reporting in Registration Callbacks

Modifying the registrationProgressing and
registrationConnected callbacks to have a parameter
for IMS Radio Access Technology information.
Through this, frameworks is aware of the IMS
RAT - LTE or WiFi - and can use the information
to display appropriate UI notifications.

Bug: 21902225
Change-Id: I18af9c146be06d98f9ea9cd9c947e4cffee04a42