Operations - Environment should also understand Kubernetes stateful sets

Problem to solve

Currently, GitLab is able to show pods that are deployed to Kubernetes per environment. Most probably it calls the Kubernetes API to retrieve the deployment for a given namespace.

However, if a project is being deployed as a stateful set, there are no deployments available and the pods aren't being shown.

Further details

Not all solutions can be deployed using deployments and replica sets. Sometimes it is required to use a stateful set.

Proposal

Either call both deployment API and stateful set API, or let the user specify if the project is deployed using a deployment or a stateful set (preferred). Everything else will remain the same.