Inject agentw in workspace

What does this MR do and why?

• Save workspaces agent config with workspaces proxy options when agentk requests config for remote development.
• Fix bug in workspace model where workspace_tokens were not getting destroyed when the workspace's desired_state changed from running.
• Create a singleton class to handle workspace url helper.
• Update the workspace tools image to the latest one which contains agentw.
• Inject and start agentw inside workspace if required.

References

• Inject agentw in workspace (#569402 - closed)

Screenshots or screen recordings

Screen_Recording_2025-09-11_at_9.02.44_PM

How to set up and validate locally

1. Setup dnsmasq for pointing workspaces.gdk.test and its subdomains to the listen_address (172.16.123.1). There is a separate issue to make this part of GDK itself - GDK: Introduce dnsmasq service (gitlab-development-kit#2694)

   Click to expand for steps to setup dnsmasq

   # Reference - https://allanphilipbarku.medium.com/setup-automatic-local-domains-with-dnsmasq-on-macos-ventura-b4cd460d8cb3
   
   ## Step 1: Install and configure Dnsmasq
   
   brew install dnsmasq
   
   mkdir -pv $(brew --prefix)/etc/
   
   echo 'address=/workspaces.gdk.test/172.16.123.1' >> $(brew --prefix)/etc/dnsmasq.conf
   
   sudo brew services start dnsmasq
   
   dig x.workspaces.gdk.test @127.0.0.1
   
   ## Step 2: Create a dns resolver and test setup
   
   sudo mkdir -v /etc/resolver
   
   sudo bash -c 'echo "nameserver 127.0.0.1" > /etc/resolver/workspaces.gdk.test'
   
   sudo killall -HUP mDNSResponder
   
   ## Step 3: Verify
   
   dig x.workspaces.gdk.test

2. Generate certs for workspaces domain in your GDK directory - mkcert "*.workspaces.gdk.test"

3. Update gdk.yml

   ---
   gitlab_k8s_agent:
     agent_listen_address: gdk.test:8150
     enabled: true
     k8s_api_listen_address: gdk.test:8154
   hostname: gdk.test
   listen_address: 172.16.123.1
   nginx:
     enabled: true
     http:
       enabled: true
   workspaces:
     enabled: true

4. gdk reconfigure && gdk restart

5. Create a new workspace. Let's call it w1.

6. Set remote_development.gitlab_workspaces_proxy.http_enabled: false in your agentk configuration.

7. Create a new workspace using the above agentk. Let's call it w2.

8. Open the workspace URL

9. Verify the URL suffix of workspace w1 is what is set in agentk configuration file's remote_development.dns_zone value.

10. Verify the URL suffix of workspace w2 is what is set in GitLab's config/gitlab.yml file's workspaces.host value.

MR acceptance checklist

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