Rename inventory_sync to player_sync

The plugin syncs more than inventories now (settings, appearance, recipe
notifications), so name it for what it does. The package becomes
@clusterio/plugin-player_sync and every inventory_sync identifier follows.

A migration entrypoint renames the inventory_sync config fields, including
load_plugin, and the inventory view permission. The plugin moves
inventories.json in the database directory to player_sync.json and
storage.inventory_sync in saves to storage.player_sync itself, and closes
dialogs left open under the old GUI names on startup.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

plugins/player_sync/module/module.json

@@ -0,0 +1,4 @@
+{
+    "name": "player_sync",
+    "load": ["player_sync.lua", "gui/dialog_failed_download.lua"]
+}