Add ims registration status

Changes the below to display the "IMS registration status" menu
in Status Info setting.
1. Add a new API "isImsRegistered(int subId)" so that IMS registration
status for specific subscription is acquired.
2. Add a carrier config for the customization.

Test: manual Checked "IMS registration state" in Status Info setting
Bug: 28806101
Merged-In: I6c452c512f03cf41704b91331e44141ed3050cf9
Change-Id: I6c452c512f03cf41704b91331e44141ed3050cf9