[V3 Config] Fix unloading and implement singleton driver (#1458)

* Add the identifier as an initialization parameter

* Remove config object singleton and opt for a shared JSON datastore

* Fix bot unloading to deal with memory leaks

* Fix tests

* Fix clear all bug

redbot/core/drivers/red_base.py

@@ -2,9 +2,9 @@ __all__ = ["BaseDriver"]
 
 
 class BaseDriver:
-    def __init__(self, cog_name):
+    def __init__(self, cog_name, identifier):
         self.cog_name = cog_name
-        self.unique_cog_identifier = None  # This is set by Config's init method
+        self.unique_cog_identifier = identifier
 
     async def get(self, *identifiers: str):
         """