Prompt to install group runner on Kubernetes
### Problem to solve
When a group maintainer/owner needs CI/CD runner capacity and no shared runners exist on the instance they should be prompted to create a group runner directly from the group's CI/CD settings. We currently give instructions for how to register the group runner, but we don't make it easy to actually create one. On project CI/CD settings we already provide a button to create a runner on Kubernetes; since we support installing group runners on Kubernetes we should also provide a button to do so from the group's CI/CD settings page.
Need statement: **The user** needs a way to **to become aware of the availability of group runners for Kubernetes when no shared runners exist for the instance** so that they can **provision GitLab runners across multiple projects easier.**
### Intended users
<!-- Who will use this feature? If known, include any of the following: types of users (e.g. Developer), personas, or specific company roles (e.g. Release Manager). It's okay to write "Unknown" and fill this field in later.
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[Devon (DevOps Engineer)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#devon-devops-engineer)
### Further details
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Our current setting pages look like this, which are the only places the user is suggested to create a runner (except for the Kubernetes cluster page).
| Current project CI/CD settings | Current group CI/CD settings |
| ------ | ------ |
|  |  |
### Proposal
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1. A button and area similar to the project CI/CD settings, on the group CI/CD settings page.
### Permissions and Security
<!-- What permissions are required to perform the described actions? Are they consistent with the existing permissions as documented for users, groups, and projects as appropriate? Is the proposed behavior consistent between the UI, API, and other access methods (e.g. email replies)? -->
### Documentation
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### Testing
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### What does success look like, and how can we measure that?
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### Links / references
issue