Deprecate VolumeGroupSnapshot v1beta1, address API review comments

[leonardoce]

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:

Addresses API review comments in #1312

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Several VolumeGroupSnapshot, VolumeGroupSnapshotClass and VolumeGroupSnapshotContent fields are now immutable. The `v1beta1` VolumeGroupSnapshot API is now marked as deprecated.

[k8s-ci-robot]

Skipping CI for Draft Pull Request.
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[leonardoce]

/assign @xing-yang

[xing-yang]

/assign @msau42

[xing-yang]

For VolumeGroupSnapshotRef in VolumeGroupSnapshotContentSpec, we can't make VolumeGroupSnapshotRef itself immutable because name and namespace are set by the admin and UID is set by the controller for static provisioning.
Can we add rule to make sure name, namespace, or UID is immutable once set?

[leonardoce]

For VolumeGroupSnapshotRef in VolumeGroupSnapshotContentSpec, we can't make VolumeGroupSnapshotRef itself immutable because name and namespace are set by the admin and UID is set by the controller for static provisioning. Can we add rule to make sure name, namespace, or UID is immutable once set?

I added a CEL rule for that.

[msau42]

Do we have tests running for the groupsnapshot functionality?

[xing-yang]

Do we have tests running for the groupsnapshot functionality?

Yes, we added e2e test before moving group snapshot to v1beta1.

[xing-yang]

@leonardoce can you add cel tests for changes you made in this PR? https://github.com/kubernetes-csi/external-snapshotter/tree/master/client/hack/cel-tests

[leonardoce]

can you add cel tests for changes you made in this PR? https://github.com/kubernetes-csi/external-snapshotter/tree/master/client/hack/cel-tests

I added the test cases. Thanks!

[msau42]

/lgtm

[xing-yang]

/lgtm
/approve

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