Move old API definitions into this repo

[inteon]

We removed the deprecated cert-manager APIs from the cert-manager/cert-manager repo (see https://github.com/cert-manager/cert-manager/pull/7278). Now, we have to move them to this repo so we can keep using them in the convert command.

The API versions that we moved are:

(acme.)cert-manager.io/v1alpha2
(acme.)cert-manager.io/v1alpha3
(acme.)cert-manager.io/v1beta1

[cert-manager-prow[bot]]

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