Automatic merge from submit-queue (batch tested with PRs 54071, 58393). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
promote aggregation API to v1
Finishing https://github.com/kubernetes/features/issues/263 as discussed in apimachinery
The API has been available since 1.6 and beta since 1.7. Openshift has been using it for about a year and service catalog (@pmorie) and metrics server (@piosz @DirectXMan12) have both been using too. The feature and the API have both been stable over that time.
@kubernetes/sig-api-machinery-api-reviews @kubernetes/api-approvers
/assign lavalamp
/assign smarterclayton
```release-note
Promoting the apiregistration.k8s.io (aggregation) to GA
```
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