Move getNetworkCountryIso impl from TM to PIM.

This moves the implementation of getNetworkCountryIso from
TelephonyManager into PhoneInterfaceManager so that we can perform an
additional IWLAN check.

Bug: 63050313
Test: no compilation errors
Merged-In: I64f31d111213281edeaeda6a09b163b860261b2d
Change-Id: I541b445b410329798acdaaaccc50955cd1574ae2