Fast Filament Change temperature check (#18738)

Marlin/src/feature/pause.cpp

  *
  * Returns 'true' if heating was completed, 'false' for abort
  */
-static bool ensure_safe_temperature(const PauseMode mode=PAUSE_MODE_SAME) {
+static bool ensure_safe_temperature(const bool wait=true, const PauseMode mode=PAUSE_MODE_SAME) {
 
   #if ENABLED(PREVENT_COLD_EXTRUSION)
     if (!DEBUGGING(DRYRUN) && thermalManager.targetTooColdToExtrude(active_extruder)) {
     UNUSED(mode);
   #endif
 
-  return thermalManager.wait_for_hotend(active_extruder);
+  if (wait)
+    return thermalManager.wait_for_hotend(active_extruder);
+
+  while (ABS(thermalManager.degHotend(active_extruder) - thermalManager.degTargetHotend(active_extruder)) > TEMP_WINDOW)
+    idle();
+
+  return true;
 }
 
 /**
 ) {
   TERN(HAS_LCD_MENU,,UNUSED(show_lcd));
 
-  if (!ensure_safe_temperature(mode)) {
+  if (!ensure_safe_temperature(false, mode)) {
     #if HAS_LCD_MENU
       if (show_lcd) lcd_pause_show_message(PAUSE_MESSAGE_STATUS, mode);
     #endif
     constexpr float mix_multiplier = 1.0;
   #endif
 
-  if (!ensure_safe_temperature(mode)) {
+  if (!ensure_safe_temperature(false, mode)) {
     #if HAS_LCD_MENU
       if (show_lcd) lcd_pause_show_message(PAUSE_MESSAGE_STATUS);
     #endif
       HOTEND_LOOP() thermalManager.reset_hotend_idle_timer(e);
 
       // Wait for the heaters to reach the target temperatures
-      ensure_safe_temperature();
+      ensure_safe_temperature(false);
 
       // Show the prompt to continue
       show_continue_prompt(is_reload);
   // Unretract
   unscaled_e_move(PAUSE_PARK_RETRACT_LENGTH, feedRate_t(PAUSE_PARK_RETRACT_FEEDRATE));
 
+  ensure_safe_temperature();
+
   // Intelligent resuming
   #if ENABLED(FWRETRACT)
     // If retracted before goto pause