Added slot index version of getNetworkCountryIso

Added this API to get network country ISO so in SIM
absent case, we can get the information from the 2nd
phone.

Bug: 141128426
Test: CTS
Merged-In: I49a55a5b549c15c55ffe1cd830a3c580eec3cff9
Change-Id: I49a55a5b549c15c55ffe1cd830a3c580eec3cff9
(cherry picked from commit c4729a41)