Support Different Storage Targets for KubeVirt Provider

[moadqassem]

What this PR does / why we need it:
Currently, machine controller only supports the creation of KubeVirt Data Volumes using PVCs without specifying what storage profile will be used which is quite important for some CSI drivers.
Which issue(s) this PR fixes:

Fixes #

What type of PR is this?
/kind feature

Special notes for your reviewer:
This PR was tested manually with KubeVirt and two machine have been created and they were reflected correctly on the VMs:

spec:
  dataVolumeTemplates:
  - metadata:
      creationTimestamp: null
      name: dv-test-557f6b6c88-2z7g2
    spec:
      source:
        http:
          url: http://remote/host/os
      storage:
        accessModes:
        - ReadWriteOnce
        resources:
          requests:
            storage: 25Gi
        storageClassName: nfs

Does this PR introduce a user-facing change? Then add your Release Note here:

support `storage ` as a another KubeVirt DataVolume storage definition 

Documentation:

None

[kubermatic-bot]

LGTM label has been added.

Git tree hash: dbc9edae3ad76e77a25c6fe174be5dc3cd8eafcd

[yaa110]

/approve
/lgtm

[kubermatic-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: yaa110

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[yaa110]

/lgtm