[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/group_test.go

@@ -369,7 +369,7 @@ func initTestGroupAccount(am *DefaultAccountManager) (*DefaultAccountManager, *t
 		Id:         "example user",
 		AutoGroups: []string{groupForUsers.ID},
 	}
-	account := newAccountWithId(context.Background(), accountID, groupAdminUserID, domain)
+	account := newAccountWithId(context.Background(), accountID, groupAdminUserID, domain, false)
 	account.Routes[routeResource.ID] = routeResource
 	account.Routes[routePeerGroupResource.ID] = routePeerGroupResource
 	account.NameServerGroups[nameServerGroup.ID] = nameServerGroup