[release-7.0]: Fix detecting default annotation on VolumeGroupSnapshotClass

[Madhu-1]

The IsDefaultAnnotation() function has been extended to check for the correct default annotation, taking the Kind of the object into consideration.

(cherry picked from commit aa837d1ddfc7a04d74dd533e2e32f6a6cc43ae70)

What type of PR is this?

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What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Cherry-pick from PR [#1015](https://github.com/kubernetes-csi/external-snapshotter/pull/1015) Adding the annotation `groupsnapshot.storage.kubernetes.io/is-default-class=true` on a VolumeGroupSnapshotClass will cause that VolumeGroupSnapshotClass to be used by default.

[Madhu-1]

/assign @xing-yang

[k8s-ci-robot]

Hi @Madhu-1. Thanks for your PR.

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[xing-yang]

/ok-to-test

[xing-yang]

/lgtm /approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Madhu-1, xing-yang

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