Implement a GraphQL subscription API to track a workspace’s state
### Problem statement
* A Workspace’s state changes over time.
* The workspaces list should always display a workspace’s current state real-time
### Solution
Implement a GraphQL subscription that allows tracking a Workspace’s state in real-time. There is a ~frontend issue to enhance the Workspaces UI so it uses the GraphQL subscription to display a workspace’s state change in real time: https://gitlab.com/gitlab-org/gitlab/-/issues/408378
Here is a branch pointing to a commit prior to removal of the subscription logic and placeholder UI from the `remote_dev` integration branch: https://gitlab.com/gitlab-org/gitlab/-/tree/caw-remote_dev-snapshot-before-placeholder-ui-removal
issue