[K8SPXC-654] Add support for Workload Identity Authentication

[spron-in]

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Tell us about the feature Instead of specifying GCS keys rely on Workload Identity.

Which product(s) is this request for? PXC, Operators

Tell us about the problem Authorization to upload backups to GCS without providing the keys

Describe alternatives you've considered Auth with keys

Additional context Anything else that you think might be useful

[Quarky9]

Similar support would be great for AWS via OIDC IAM roles. All thats missing for AWS at least would be the ability to add custom ENV and Volumes to the backup job pod