[V3 Mod/Modlog] prevent self-casing the bot + feedback for heirarchy (#1777)

* prevent the bot from being a modlog target

* prevent heirarchy issues in mod

* modify this comparison to avoid more complex mocking of the guild object in mod test

* spelling

redbot/core/modlog.py

@@ -461,6 +461,9 @@ async def create_case(
     if not await case_type.is_enabled():
         return None
 
+    if user == bot.user:
+        return None
+
     next_case_number = int(await get_next_case_number(guild))
 
     case = Case(