feat(hero): 新增英雄按等级切换不同颜色描边的功能

新增紫色描边shader与对应材质资源，为英雄预制体注册四种颜色描边材质
重构FlashSprite组件支持按等级切换描边，在英雄初始化与升级时自动更新描边样式

assets/resources/game/heros/ha1.prefab

@@ -292,6 +292,22 @@
       "__uuid__": "8eee8ab1-fe48-4b22-b956-3f5c18fc4810",
       "__expectedType__": "cc.Material"
     },
+    "outlineMatGreen": {
+      "__uuid__": "ded728b9-6dd0-4c37-9970-9745c62aa8bf",
+      "__expectedType__": "cc.Material"
+    },
+    "outlineMatBlue": {
+      "__uuid__": "0f38817f-a8df-4547-8b37-e7ed29de8216",
+      "__expectedType__": "cc.Material"
+    },
+    "outlineMatPurple": {
+      "__uuid__": "acf230af-e9ae-42f8-80a1-552d7d10390f",
+      "__expectedType__": "cc.Material"
+    },
+    "outlineMatYellow": {
+      "__uuid__": "2b8a37ee-732c-4c5b-b6a4-136f3e581cde",
+      "__expectedType__": "cc.Material"
+    },
     "_id": ""
   },
   {