Move Stepper::synchronize to Planner (#10713)

Co-Authored-By: ejtagle <ejtagle@hotmail.com>

Marlin/src/module/planner.cpp

@@ -1299,6 +1299,11 @@ void Planner::check_axes_activity() {
 
 #endif // PLANNER_LEVELING
 
+/**
+ * Block until all buffered steps are executed / cleaned
+ */
+void Planner::synchronize() { while (has_blocks_queued() || stepper.cleaning_buffer_counter) idle(); }
+
 /**
  * Planner::_buffer_steps
  *