Rename the GitLab (Kubernetes) Agent
## Goal
Following https://gitlab.com/gitlab-com/legal-and-compliance/-/issues/671#note_737469446 we need to rename the GitLab Kubernetes Agent
## Proposed new name
| Old | New |
| --- | --- |
| GitLab Kubernetes Agent | *GitLab Agent for Kubernetes* |
GitLab Kubernetes Agent Server (KAS) | *GitLab Agent Server* (KAS) |
| Kubernetes secret | *Agent secret* |
| Kubernetes Agent configuration repository | *Agent configuration repository* |
### Attribution
We'll also need to include attribution for the use of the Kubernetes trademark as follows:
> [Kubernetes](https://kubernetes.io/) is a registered trademark of The Linux Foundation.
## Scope
- [x] Every reference in [the agent repo](https://gitlab.com/gitlab-org/cluster-integration/gitlab-agent/)
- [x] Every reference in [the docs](https://docs.gitlab.com/ee/user/clusters/agent/)
- [x] Every reference in the GitLab UI
- [x] Every reference in the GDK
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