Core: add race mode to multidata and datastore (#4017)

* add race mode to multidata and datastore

* have commonclient check race mode on connect and add it to the tooltip ui

MultiServer.py

@@ -427,6 +427,8 @@ class Context:
               use_embedded_server_options: bool):
 
         self.read_data = {}
+        # there might be a better place to put this.
+        self.stored_data["race_mode"] = decoded_obj.get("race_mode", 0)
         mdata_ver = decoded_obj["minimum_versions"]["server"]
         if mdata_ver > version_tuple:
             raise RuntimeError(f"Supplied Multidata (.archipelago) requires a server of at least version {mdata_ver},"