API mirroring annotations not registered or documented

**This is a Bug Report**

**Problem:**
Kubernetes sets up to ~three~ four annotations when mirroring a resource (for example, a [mirror pod](https://kubernetes.io/docs/concepts/workloads/pods/#static-pods)). These are:

- `kubernetes.io/config.source`
- `kubernetes.io/config.seen`
- `kubernetes.io/config.hash`
- `kubernetes.io/config.mirror`

However, those annotations are not documented in
https://kubernetes.io/docs/reference/labels-annotations-taints/

**Proposed Solution:**
Document those annotations.

**Page to Update:**
https://kubernetes.io/docs/reference/labels-annotations-taints/

**Additional Information:**
See https://pkg.go.dev/k8s.io/kubernetes/pkg/kubelet/types for more details on the values that the kubelet sets for `kubernetes.io/config.source`. I don't think we promise that the kubelet is the only thing that ever sets this annotation, though.

/sig architecture
/sig node
/language en