Normalize load/unload length in M600

Marlin/Marlin_main.cpp

   #endif
 
   void do_pause_e_move(const float &length, const float fr) {
-    current_position[E_AXIS] += length;
+    current_position[E_AXIS] += length * 100.0 / flow_percentage[active_extruder] / volumetric_multiplier[active_extruder];
     set_destination_from_current();
     RUNPLAN(fr);
     stepper.synchronize();
           SERIAL_ECHOLNPGM(MSG_ERR_COLD_EXTRUDE_STOP);
         }
         #if ENABLED(PREVENT_LENGTHY_EXTRUDE)
-          if (destination[E_AXIS] - current_position[E_AXIS] > EXTRUDE_MAXLENGTH) {
+          if (fabs(destination[E_AXIS] - current_position[E_AXIS]) > EXTRUDE_MAXLENGTH / volumetric_multiplier[active_extruder]) {
             current_position[E_AXIS] = destination[E_AXIS]; // Behave as if the move really took place, but ignore E part
             SERIAL_ECHO_START();
             SERIAL_ECHOLNPGM(MSG_ERR_LONG_EXTRUDE_STOP);

Marlin/planner.cpp

         SERIAL_ECHOLNPGM(MSG_ERR_COLD_EXTRUDE_STOP);
       }
       #if ENABLED(PREVENT_LENGTHY_EXTRUDE)
-        if (labs(de) > (int32_t)axis_steps_per_mm[E_AXIS_N] * (EXTRUDE_MAXLENGTH)) { // It's not important to get max. extrusion length in a precision < 1mm, so save some cycles and cast to int
+        int32_t de_mm = labs(de * volumetric_multiplier[active_extruder]);
+        if (de_mm > (int32_t)axis_steps_per_mm[E_AXIS_N] * (EXTRUDE_MAXLENGTH)) { // It's not important to get max. extrusion length in a precision < 1mm, so save some cycles and cast to int
           position[E_AXIS] = target[E_AXIS]; // Behave as if the move really took place, but ignore E part
           de = 0; // no difference
           #if ENABLED(LIN_ADVANCE)