Added REST based API calls for GCS as gsutil isn't supported for s390x in bootstrap image

[chandramerla]

This is a pre-requisite for enabling publishing jobs for k8s provider for s390x (#3566 ), as those jobs need to interact with gcs from s390x machines

What this PR does / why we need it:

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 #

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Checklist

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• [ ] Design: A design document was considered and is present (link) or not required
• [x] PR: The PR description is expressive enough and will help future contributors
• [ ] Code: Write code that humans can understand and Keep it simple
• [ ] Refactor: You have left the code cleaner than you found it (Boy Scout Rule)
• [ ] Upgrade: Impact of this change on upgrade flows was considered and addressed if required
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NONE