🚸 Indicate Preheating for probe / leveling (#23088)

Marlin/src/lcd/language/language_en.h

   LSTR MSG_ERR_MINTEMP                    = _UxGT("Err: MINTEMP");
   LSTR MSG_HALTED                         = _UxGT("PRINTER HALTED");
   LSTR MSG_PLEASE_RESET                   = _UxGT("Please Reset");
+  LSTR MSG_PREHEATING                     = _UxGT("Preheating...");
   LSTR MSG_HEATING                        = _UxGT("Heating...");
   LSTR MSG_COOLING                        = _UxGT("Cooling...");
   LSTR MSG_BED_HEATING                    = _UxGT("Bed Heating...");

Marlin/src/module/probe.cpp

       #define WAIT_FOR_BED_HEAT
     #endif
 
+    LCD_MESSAGE(MSG_PREHEATING);
+
     DEBUG_ECHOPGM("Preheating ");
 
     #if ENABLED(WAIT_FOR_NOZZLE_HEAT)