Automatic merge from submit-queue
Deprecate Deployment .spec.rollbackTo field
~Depends on #48746~ (merged)
xref: #46934, #49135
1. Deprecate Deployment field `.spec.rollbackTo` in `extensions/v1beta1` and `apps/v1beta1`, and remove the same field and `/rollback` endpoint from `apps/v1beta2` Deployment.
1. Add an annotation `deprecated.deployment.rollback.to` in `apps/v1beta2` for conversion to/from other versions.
Note: `apps/v1beta2` is new in 1.8 (and WIP), so it is okay to make breaking changes to it.
```release-note
Deprecate Deployment .spec.rollbackTo field
```
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