feat: Added toString method to all the drags events message handlers (#2014)

Added toString method to all Drag Event message Handlers in flame/lib/src/events/messages/ which were returning pure data objects and were not much meaningful

tutorials/space_shooter/lib/steps/1_getting_started/1_flame_game/code.dart

@@ -4,7 +4,6 @@ import 'package:flutter/material.dart';
 
 class Player extends PositionComponent {
   static final _paint = Paint()..color = Colors.white;
-
   @override
   void render(Canvas canvas) {
     canvas.drawRect(size.toRect(), _paint);