[management] Add option to disable default all-to-all policy (#3970)

This PR introduces a new configuration option `DisableDefaultPolicy` that prevents the creation of the default all-to-all policy when new accounts are created. This is useful for automation scenarios where explicit policies are preferred.
### Key Changes:
- Added DisableDefaultPolicy flag to the management server config
- Modified account creation logic to respect this flag
- Updated all test cases to explicitly pass the flag (defaulting to false to maintain backward compatibility)
- Propagated the flag through the account manager initialization chain

### Testing:

- Verified default behavior remains unchanged when flag is false
- Confirmed no default policy is created when flag is true
- All existing tests pass with the new parameter

management/server/store/sql_store_test.go

@@ -2044,7 +2044,7 @@ func newAccountWithId(ctx context.Context, accountID, userID, domain string) *ty
 		},
 	}
 
-	if err := acc.AddAllGroup(); err != nil {
+	if err := acc.AddAllGroup(false); err != nil {
 		log.WithContext(ctx).Errorf("error adding all group to account %s: %v", acc.Id, err)
 	}
 	return acc