Add snapshot size to VSC created for VGS

[Madhu-1]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespaces from that line:

/kind api-change

/kind bug

/kind cleanup /kind design /kind documentation /kind failing-test /kind feature /kind flake

What this PR does / why we need it:

Currently the RestoreSize is missing when the corresponding VSC are created for the the volumesnapshotgroup, This PR adds the missing RestoreSize for VSC.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

NONE

[k8s-ci-robot]

Hi @Madhu-1. Thanks for your PR.

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: Madhu-1 Once this PR has been reviewed and has the lgtm label, please assign xing-yang for approval. For more information see the Kubernetes Code Review Process.

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Needs approval from an approver in each of these files: - **[OWNERS](https://github.com/kubernetes-csi/external-snapshotter/blob/master/OWNERS)** Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[Madhu-1]

/assign @xing-yang /assign @nixpanic

[Madhu-1]

/hold