Add version field to the OpenAPI definition

[dollierp]

What this PR does / why we need it:
This missing field is reported by ZAP when trying to discover the CDI API: error: attribute info.version is missing.

Adding this field makes ZAP happy and the scan can proceed.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes https://issues.redhat.com/browse/CNV-34683

Special notes for your reviewer:

I copied KubeVirt implementation (https://github.com/kubevirt/kubevirt/blob/5d8c225/pkg/virt-api/api.go#L728)

Release note:

NONE

[akalenyu]

/lgtm
/cc @mhenriks
does it make sense to include the version in api/openapi-spec/swagger.json?

[dollierp]

/retest

[mhenriks]

/approve

[kubevirt-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: mhenriks

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[akalenyu]

/retest

[akalenyu]

/test pull-containerized-data-importer-e2e-upg

[dollierp]

/retest

[akalenyu]

/cherrypick release-v1.58

[kubevirt-bot]

@akalenyu: new pull request created: #3014

In response to this:

/cherrypick release-v1.58

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