Add heater timeouts to ExtUI (#13970)

- Add local UI methods to get heater timeout state.
- Add methods to resume timed-out heaters.
- Re-enable heaters on UI temperature request.
- Make `ExtUI` show a dialog box if pause needs a button press after reheat.

Marlin/src/lcd/extensible_ui/ui_api.h

@@ -70,6 +70,11 @@ namespace ExtUI {
   void enqueueCommands_P(PGM_P const);
   bool commandsInQueue();
 
+  bool isHeaterIdle(const heater_t);
+  bool isHeaterIdle(const extruder_t);
+  void enableHeater(const heater_t);
+  void enableHeater(const extruder_t);
+
   /**
    * Getters and setters
    * Should be used by the EXTENSIBLE_UI to query or change Marlin's state.