Begin work on a data request API (#4045)

[Core] Data Deletion And Disclosure APIs

 - Adds a Data Deletion API
   - Deletion comes in a few forms based on who is requesting
   - Deletion must be handled by 3rd party
 - Adds a Data Collection Disclosure Command
   - Provides a dynamically generated statement from 3rd party
   extensions
 - Modifies the always available commands to be cog compatible
   - Also prevents them from being unloaded accidentally

redbot/cogs/cleanup/cleanup.py

@@ -25,6 +25,10 @@ class Cleanup(commands.Cog):
         super().__init__()
         self.bot = bot
 
+    async def red_delete_data_for_user(self, **kwargs):
+        """ Nothing to delete """
+        return
+
     @staticmethod
     async def check_100_plus(ctx: commands.Context, number: int) -> bool:
         """