Allow setting max hours before termination

What does this MR do and why?

Adds a numeric field to the workspace creation form that allows customizing after how many hours the workspace automatically terminates.

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. Click the "New Workspace" button.
5. Select a project with cluster agents set up. I you haven’t you will have to configure your GDK to run the k8s cluster agent https://gitlab.com/gitlab-org/remote-development/gitlab-remote-development-docs/-/blob/main/doc/local-development-environment-setup.md.
6. You should see the max hours before termination field.

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 #408377 (closed)