MSIM: set phone account handle changes for ECall

Add interface API between Telephony to Telecomm for
updating phoneAcount.
Currently on multisim, Telephony(PhoneApp) picks the best
possible sub for placing emergency call, after selecting the
best possible sub, Telephony uses this new interface API to update
the phoneAcount handle to Telecomm which inturn helps to display
the proper subId on which ECall placed.

Change-Id: Ic0fdc01810ccc35479a1a9447c40e38122a155a9
CRs-Fixed: 722205