Add Workspace creation

What does this MR do and why?

It implements a UI to create a Workspace from the GitLab application.

Figma design

https://www.figma.com/file/2XmMH4x3cWGBTTnOJaIl6J/Remote-Development?node-id=117-5643&t=6zPwYauwre4cfIbN-0

How does the UI work?

1. A user navigates to their Workspace creation screen by selecting "New Workspace" in the Workspaces list page.
2. A user selects a project.
   1. The UI displays an alert indicating that the project lacks associated cluster agents.
   2. The UI displays an alert indicating if the project doesn’t contain a .devfile in its repository tree.
3. The user selects a cluster agent.
4. The user selects "Create Workspace" to create the workspace.
5. The UI navigates to the Workspace URL if creating a workspace succeeds.

This MR represents the following work:

• Create a Workspace from Gitlab UI (#385142 - closed)

Screenshots or screen recordings

Demo	create_workspace_demo
No devfile or agents

How to set up and validate locally

1. Enable the remote development flag

   Feature.enable(:remote_development_feature_flag)

2. Ensure you have a valid Ultimate License for your GDK instance.

3. Follow the instructions to set up remote development in your local environment: https://gitlab.com/gitlab-org/remote-development/gitlab-remote-development-docs/-/blob/main/doc/local-development-environment-setup.md. You need to have at least one cluster agent associated with a group to the entire workflow.

4. After checking out the branch, you might need to restart the GDK rails server: gdk restart rails.

5. Visit "Your Dashboard" i.e. http://localhost:3000/.

6. Click the Workspaces sidebar entry under "My Work".

7. Click the New Workspace button.

8. Interact with the Workspace form.

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 work #385142 (closed)