Add pods page to the Kubernetes dashboard - preparation

What does this MR do and why?

In order to keep the iterations small, this MR introduces some preparation work:

• create a view for the dashboard#show action
• create a Vue router
• add pods page (with no custom data for now)
• add common components - page title and the agent area.

Screenshots or screen recordings

Just a tiny bit of an actual content for now:

How to set up and validate locally

Full set up

1. Enable the k8s_dashboard feature flag

      Feature.enable(:k8_watch_api)

2. Enable KAS on your GDK (steps 1-2 from the guide).

3. Visit the Project -> Infrastructure -> Kubernetes clusters page and create an agent following the instruction from the modal.

   • Select the "Connect a cluster" button
   • The modal should pop up
   • In the modal select "Select an agent or enter a name to create new"
   • You probably won't have any configured agents to show up in the list, create a new one by typing the name of your choice
   • The button should appear at the bottom of the list saying "Create agent: <your-agent-name>"
   • Select the button and click "Register" in the next view.
   • Save the token to use it in the next point.

4. Add the following configuration inside your project in .gitlab/agents/<your-agent-name>/config.yaml for the user_access agent:

   gitops:
     manifest_projects:
     - id: <your-group>/<your-project>
   user_access:
     access_as: 
       agent: {}
     projects:
     - id: <your-group>/<your-project-to-share-agent-with>

5. Note that the shared agents should be connected to the cluster in order to appear in the list. Please follow points 3-8 from the guide and then the (Optional) Deploy the GitLab Agent (agentk) with k3d section to create a local cluster and connect your agent with the cluster.

6. Navigate to https://gdk.test:3443/-/kubernetes//pods

7. Verify the title area for the pods page

Alternative set up

1. Enable the k8s_dashboard feature flag

      Feature.enable(:k8_watch_api)

2. Run the following in the rails console: FactoryBot.create(:cluster_agent, project: Project.last)
3. Navigate to https://gdk.test:3443/-/kubernetes//pods
4. Verify the title area for the pods page

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.

Review progress:

• backend developer review
• backend maintainer review
• frontend developer review
• frontend maintainer review

Related to #428312 (closed)