[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/management_proto_test.go

@@ -444,7 +444,7 @@ func startManagementForTest(t *testing.T, testFile string, config *types.Config)
 	permissionsManager := permissions.NewManager(store)
 
 	accountManager, err := BuildManager(ctx, store, peersUpdateManager, nil, "", "netbird.selfhosted",
-		eventStore, nil, false, MocIntegratedValidator{}, metrics, port_forwarding.NewControllerMock(), settingsMockManager, permissionsManager)
+		eventStore, nil, false, MocIntegratedValidator{}, metrics, port_forwarding.NewControllerMock(), settingsMockManager, permissionsManager, false)
 
 	if err != nil {
 		cleanup()