Upload attestations and print cosign version

[upodroid]

This change uploads the attesttation payload so we can view it with the job it was built from and we can see more clearly the cosign version we used.

/cc @kvmware

[knative-prow[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

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[upodroid]

this can be merged now

[krsna-m]

/lgtm