Allow excluding workspaces with "terminated" actual state in Workspaces GraphQL API

Problem statement

In #395517 (closed), we are implementing a UI that allows users to view and manage workspaces for the project they are seeing in the Repository view. We don‘t want to display terminated workspaces in this UI because it exists in a very constrained space: The "Edit" dropdown.

Solution proposal

Add a filter to the current user workspaces GraphQL API that allows retrieving workspaces that are not terminated.