UI: Workspaces agent admin view

Issue: UI: Introduce an admin view providing visibilit... (#419281 - closed)

What does this MR do and why?

Implements UI: Introduce an admin view providing visibilit... (#419281 - closed), excluding the exceptions mentioned in #419281 (comment 1710803314)+

See overview of Category:Remote Development Workspaces Admin UI issues and MRs in MVP of Admin UI for Workspaces (&11992 - closed)

Screenshots or screen recordings

How to set up and validate locally

1. Create a project that has an agent configured, and workspaces created for the agent
2. Log in as an agent admin (a maintainer on the agent project)
3. Go to the project -> Kubernetes Clusters
4. Select new Workspaces tab
5. Verify only workspaces for that agent are shown (not for other agents)
6. Verify that actions such as stop and terminate can be taken on the workspaces.

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.