Design: Kubernetes Agent - Add Agent installation instructions in the UI
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### Overview
Enable users that have navigated to the Kubernetes UIs to be able to install a new Agent without navigating to the documentation and having to switch between GitLab UI, CLI and documentation.
### Proposal
Provide the basic Agent installation instructions in the Agent listing page.
|Empty state (disabled if no agent directory)| Empty state | Select Agent | Agent selected | Registering Agent | Generating token | Installation instructions|
|-----------| ----------- | ----------- | ----------- | ----------- | ----------- |----|
| | |  |  | | | 
**Errors**
|Agent failed to register| Token failed to be generated|
|---|-----|
| | |
### Related issues
[Design - Import cluster GUI with agent setup](https://gitlab.com/gitlab-org/gitlab/-/issues/225226/)
[Figma file](https://www.figma.com/file/2U5VzLV4jGw59Eghim2sN3/Kubernetes-Agent-Add-Agent-installation-instructions-in-the-UI-321408?node-id=140%3A24651)
issue