feat(gui): add ebox prefab reference to mission prefab

新增了ebox预制体资源，并将其关联到mission预制体中，补充任务界面的装备箱相关UI元素

assets/resources/gui/element/mission.prefab

@@ -68,10 +68,13 @@
       },
       {
         "__id__": 3234
+      },
+      {
+        "__id__": 3236
       }
     ],
     "_prefab": {
-      "__id__": 3236
+      "__id__": 3238
     },
     "_lpos": {
       "__type__": "cc.Vec3",
@@ -61425,6 +61428,28 @@
     "__type__": "cc.CompPrefabInfo",
     "fileId": "08cRUjxXhBTb80XPuG1XkA"
   },
+  {
+    "__type__": "da70cWddIFAWrAp8y0Z3tP6",
+    "_name": "",
+    "_objFlags": 0,
+    "__editorExtras__": {},
+    "node": {
+      "__id__": 1
+    },
+    "_enabled": true,
+    "__prefab": {
+      "__id__": 3237
+    },
+    "equip_box": {
+      "__uuid__": "66d7902d-2a85-43d5-8cbb-671cc7dbb275",
+      "__expectedType__": "cc.Prefab"
+    },
+    "_id": ""
+  },
+  {
+    "__type__": "cc.CompPrefabInfo",
+    "fileId": "92T2HyCYRIT5ZAbyLMEEkH"
+  },
   {
     "__type__": "cc.PrefabInfo",
     "root": {