Deprecate DV garbage collection (#3197)

After several releases with GC disabled by default, we decided to
deprecate it, as unfortunately it violates fundamental principle of
Kubernetes. CR should not be auto-deleted when it completes its role
(Job with TTLSecondsAfterFinished is an exception), and once CR was
created we can assume it is there until explicitly deleted. In addition,
CR should keep idempotency, so the same CR manifest can be applied
multiple times, as long as it is a valid update (e.g. DataVolume
validation webhook does not allow updating the spec).

Signed-off-by: Arnon Gilboa <agilboa@redhat.com>

docs/cluster-configuration.md

@@ -1328,28 +1328,6 @@ metadata:
         }
       ]
 ```
-##### Disable DataVolume garbage collection
-To disable [DataVolume garbage collection](https://github.com/kubevirt/containerized-data-importer/blob/main/doc/datavolumes.md#garbage-collection-of-successfully-completed-datavolumes), the following annotation should be added to the HyperConverged CR:
-```yaml
-metadata:
-  annotations:
-    containerizeddataimporter.kubevirt.io/jsonpatch: |-
-      [
-        {
-          "op": "add",
-          "path": "/spec/config/dataVolumeTTLSeconds",
-          "value": -1
-        }
-      ]
-```
-Or from CLI:
-```bash
-$ kubectl annotate --overwrite -n kubevirt-hyperconverged hco kubevirt-hyperconverged \
-  containerizeddataimporter.kubevirt.io/jsonpatch='[{"op": "add", \
-    "path": "/spec/config/dataVolumeTTLSeconds", \
-    "value": -1 }]'
-```
-To enable DataVolume garbage collection put any non-negative value for the `dataVolumeTTLSeconds`, which is the time in seconds after DataVolume completion it can be garbage collected.
 ##### Modify DataVolume Upload URL
 The user wants to override the default URL used when uploading to a DataVolume, by setting the CDI CR's `spec.config.uploadProxyURLOverride` to `myproxy.example.com`. In order to do that, the following annotation should be added to the HyperConverged CR:
 ```yaml