Automatic merge from submit-queue
[GarbageCollector] Allow per-resource default garbage collection behavior
What's the bug:
When deleting an RC with `deleteOptions.OrphanDependents==nil`, garbage collector is supposed to treat it as `deleteOptions.OrphanDependents==true", and orphan the pods created by it. But the apiserver is not doing that.
What's in the pr:
Allow each resource to specify the default garbage collection behavior in the registry. For example, RC registry's default GC behavior is Orphan, and Pod registry's default GC behavior is CascadingDeletion.
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