Relax volumeContentSource restriction for ROX multi-zone dynamic volume creation

[pwschuurman]

This enables empty ROX multi-zone PVCs to be created, to allow for static hydration of disks

What type of PR is this?

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/kind api-change
/kind bug
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/kind failing-test
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What this PR does / why we need it: Currently ROX multi-zone volumes can only be created from a volume source (eg: snapshot/disk image). This limits the flexibility of a user that wants to create a ROX multi-zone volume which is empty, and then write the same data individually to each created disk. This allows all disks to share the same name (as they are part of a "multi-zone" volume), but have data populated without needing to pre-create a snapshot/disk image (as copying data directly to each individual disk in parallel can be faster than creating and restoring from a snapshot).

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

Relax multi-zone volume ROX restriction when creating a volume without a volumeContentSource.

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This pull-request has been approved by: pwschuurman

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[pwschuurman]

/retest

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/retest

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/retest

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/retest

[k8s-ci-robot]

@pwschuurman: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-gcp-compute-persistent-disk-csi-driver-unit	7f86194	link	true	/test pull-gcp-compute-persistent-disk-csi-driver-unit
pull-gcp-compute-persistent-disk-csi-driver-e2e-windows-2022	7f86194	link	false	/test pull-gcp-compute-persistent-disk-csi-driver-e2e-windows-2022
pull-gcp-compute-persistent-disk-csi-driver-e2e-windows-2019	7f86194	link	false	/test pull-gcp-compute-persistent-disk-csi-driver-e2e-windows-2019
pull-gcp-compute-persistent-disk-csi-driver-e2e	7f86194	link	true	/test pull-gcp-compute-persistent-disk-csi-driver-e2e
pull-gcp-compute-persistent-disk-csi-driver-kubernetes-integration	7f86194	link	true	/test pull-gcp-compute-persistent-disk-csi-driver-kubernetes-integration

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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