Merge "Add a carrier attribute (iccid prefix) for carrier id proto"

  // "content://telephony/carriers/preferapn" on device.

  // Sample values: fast.t-mobile.com, internet

  repeated string preferred_apn = 7;

  // [Optional] Prefix of Integrated Circuit Card Identifier. Read from subscription EF_ICCID.

  // Sample values: 894430, 894410

  repeated string iccid_prefix = 8;

};