add private volumeGroupSnapshotClass Api

[ShravaniVangur]

Updating the ocs-operator to import the private volumegroupsnapshotclass api,enabling access to and utilization of the private fork of the sidecar available at https://github.com/red-hat-storage/external-snapshotter.

//Waiting for the controllers to be available before merging.
//Pending- dependency update

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PR needs rebase.

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