Improve handling of conditional order waiting loops

Do not leave station/depot/waypoint at all if conditional order
loop would result in re-starting waiting/loading

Only actually leave and update timetable at end of loop

Rate-limit loop checks regardless of timetabled wait time

src/vehicle_base.h

@@ -63,6 +63,7 @@ enum VehicleFlags {
 	VF_TIMETABLE_SEPARATION     = 14, ///< Whether timetable auto-separation is enabled
 	VF_AUTOMATE_TIMETABLE       = 15, ///< Whether the vehicle should manage the timetable automatically.
 	VF_HAVE_SLOT                = 16, ///< Vehicle has 1 or more slots
+	VF_COND_ORDER_WAIT          = 17, ///< Vehicle is waiting due to conditional order loop
 };
 
 /** Bit numbers used to indicate which of the #NewGRFCache values are valid. */