Initialize EKS clusters form for instance and group level clusters

What does this MR do?

This MR is part of delivering #22392 (closed). It does not deliver the whole feature. It only delivers the functionality described below:

A user can integrate a Kubernetes cluster at three levels in GitLab:

• Project level (Project page -> Sidebar Menu -> Operations -> Kubernetes)
• Group level (Group page -> Sidebar Menu -> Kubernetes)
• Instance level (Admin Interface -> Sidebar Menu -> Kubernetes)

This MR initializes the "Create AWS EKS Cluster" Vue app at these three levels.

No user-facing changes

• Encapsulates create_cluster initialization in a single entry point function to make easier the initialization in multiple places.

Testing

Before testing

• Enable create_eks_clusters feature flag
• Set up Google OAuth https://gitlab.com/gitlab-org/gitlab-development-kit/blob/master/doc/howto/google-oauth2.md

How to test

Open the Create cluster UI in these three places:

• Project level (Project page -> Sidebar Menu -> Operations -> Kubernetes)
• Group level (Group page -> Sidebar Menu -> Kubernetes)
• Instance level (Admin Interface -> Sidebar Menu -> Kubernetes)

If everything works correctly, you should see the following behavior in the three places:

When the user clicks Amazon EKS button, it displays Create EKS Cluster form. It changes the tab title to "Create new Cluster on EKS"

When the user clicks "Google GKE", it should be redirected to the Create GKE Cluster form.