[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/http/testing/testing_tools/tools.go

@@ -1,5 +1,4 @@
 package testing_tools
-
 import (
 	"bytes"
 	"context"
@@ -138,7 +137,7 @@ func BuildApiBlackBoxWithDBState(t TB, sqlFile string, expectedPeerUpdate *serve
 	userManager := users.NewManager(store)
 	permissionsManager := permissions.NewManager(store)
 	settingsManager := settings.NewManager(store, userManager, integrations.NewManager(&activity.InMemoryEventStore{}), permissionsManager)
-	am, err := server.BuildManager(context.Background(), store, peersUpdateManager, nil, "", "", &activity.InMemoryEventStore{}, geoMock, false, validatorMock, metrics, proxyController, settingsManager, permissionsManager)
+	am, err := server.BuildManager(context.Background(), store, peersUpdateManager, nil, "", "", &activity.InMemoryEventStore{}, geoMock, false, validatorMock, metrics, proxyController, settingsManager, permissionsManager, false)
 	if err != nil {
 		t.Fatalf("Failed to create manager: %v", err)
 	}