refactor: compose shared scenario event and item packs

resources/scenario/scenario_901.json

@@ -1,5 +1,6 @@
 {
     "title": "【공백지】 무주공산",
+    "extends": ["extensions/events/standard.json"],
     "startYear": 180,
     "map": {
         "mapName": "miniche_clean"
@@ -9,6 +10,5 @@
         "expandCityDefaultCost": 30000,
         "expandCityCostCoef": 250,
         "npcBanMessageProb": 1
-    },
-    "events": [["destroy_nation", 1000, ["and", ["Date", ">=", 183, 1], ["RemainNation", "==", 1]], ["BlockScoutAction"], ["DeleteEvent"]]]
+    }
 }