Automatic merge from submit-queue (batch tested with PRs 44424, 44026, 43939, 44386, 42914)

remove defaulting from conversion path

follow up for #42764

* remove call to defaulting from conversion path (defaulting is a separate step from conversion)
* remove non-top-level-object defaulting registration (unused after conversion call is removed)
* generate missing top-level defaults for some api groups:
  * autoscaling/v2alpha1
  * policy/v1alpha1
  * policy/v1beta1
* register top-level defaults for some api groups that were missing them:
  * autoscaling/v2alpha1
  * settings/v1alpha1