Refactor file loading to use a common class that has proper error handling.

src/util/guidance/turn_lanes.cpp

@@ -31,6 +31,11 @@ bool LaneTuple::operator==(const LaneTuple other) const
 
 bool LaneTuple::operator!=(const LaneTuple other) const { return !(*this == other); }
 
+bool LaneTupleIdPair::operator==(const LaneTupleIdPair &other) const
+{
+    return other.first == first && other.second == second;
+}
+
 } // namespace guidance
 } // namespace util
 } // namespace osrm