Do not add maistra-version label to nested resources

We're adding maistra-version label to all resources that contain a release label, which includes nested resources like pod templates in deployments. Some deployments do not specify a selector, which means these labels are included in the selector label set, which prevents updates to new versions, as the label set has changed.

There may also be other places where these were being added, e.g. pod disruption budgets.

We should only be adding this label to top level resources.