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/data/block/grass_block.toml

@@ -8,5 +8,4 @@ is_passable = false
 is_transitional = true
 is_transparent = false
 name = 'grass_block'
-name_key = 'block.grass_block'
 roughness = 0.90000000000000002