Workspaces list’s terminate action button

What does this MR do and why?

It adds a terminate action button to the Workspaces List. When the user clicks this button, GitLab will start the termination process which is asynchronous (the workspace is not terminated immediately). Clicking the button executes the workspaceUpdate mutation. The button becomes disabled and loading if the workspace is already in the termination process.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Enable the remote development feature flag Feature.enable(:remote_development_feature_flag)
2. You might need to run gdk restart rails-web so rails reconfigure the routes.
3. Open http://gdk.test:3000/-/remote_development/workspaces in your Web Browser.
4. You should see a list of workspaces like the screenshots above.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #385145 (closed)