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: Ib02e4d145cb39683bcb13d39715003095ad93eef
Change-Id: Ib02e4d145cb39683bcb13d39715003095ad93eef
(cherry picked from commit a5fedc5c)