refactor(localization): switch block translations to item naming

Remove the `name_key` field from block definitions and use item-based
localization keys (`item.*.name`) for inventory display. Item data now
stores the localized name at load time.

assets/lang/en_US.json

@@ -36,14 +36,15 @@
     "joingame.server_ip": "Server Ip",
     "joingame.join_world": "Join World",
     "error.disable_voice": "Server Disable Voice Chat",
-    "block.air": "air",
-    "block.dirt": "dirt",
-    "block.grass_block": "grass block",
-    "block.grass": "grass",
-    "block.leaf": "leaf",
-    "block.log": "log",
-    "block.sand": "sand",
-    "block.snowy_grass_block": "snowy grass block",
-    "block.stone": "stone",
-    "block.water": "water"
+    "item.air.name": "air",
+    "item.dirt.name": "dirt",
+    "item.grass_block.name": "grass block",
+    "item.grass.name": "grass",
+    "item.leaf.name": "leaf",
+    "item.log.name": "log",
+    "item.sand.name": "sand",
+    "item.snowy_grass_block.name": "snowy grass block",
+    "item.stone.name": "stone",
+    "item.water.name": "water",
+    "item.pig_spawn_egg.name": "pig spawn egg"
 }

assets/lang/zh_CN.json

@@ -36,14 +36,15 @@
     "joingame.server_ip": "服务器IP",
     "joingame.join_world": "加入世界",
     "error.disable_voice": "服务器已禁用语音聊天",
-    "block.air": "空气",
-    "block.dirt": "泥土",
-    "block.grass_block": "草方块",
-    "block.grass": "草",
-    "block.leaf": "树叶",
-    "block.log": "原木",
-    "block.sand": "沙子",
-    "block.snowy_grass_block": "覆雪草方块",
-    "block.stone": "石头",
-    "block.water": "水"
+    "item.air.name": "空气",
+    "item.dirt.name": "泥土",
+    "item.grass_block.name": "草方块",
+    "item.grass.name": "草",
+    "item.leaf.name": "树叶",
+    "item.log.name": "原木",
+    "item.sand.name": "沙子",
+    "item.snowy_grass_block.name": "覆雪草方块",
+    "item.stone.name": "石头",
+    "item.water.name": "水",
+    "item.pig_spawn_egg.name": "猪猪刷怪蛋"
 }