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
Change-Id: I64f31d111213281edeaeda6a09b163b860261b2d
(cherry picked from commit 83c25b8ce17c3ce387d87d5f36182645e686540e)