Use new Google Cloud Storage package for managing storage objects

Note from the module used for the GCS Storage API package used by the agent:

> import "google.golang.org/api/storage/v1"
>
> Package storage provides access to the Cloud Storage JSON API.
>
> This package is DEPRECATED. Use package cloud.google.com/go/storage instead.

Reporting this only because I couldn't find another issue for this, and as they say, "see something say something."

Search the repository for imports of google.golang.org/api/storage/v1 and inspect the agent's Cloud Storage object management entry points. Compare those uses with cloud.google.com/go/storage, then run the existing related tests; done means the deprecated package is no longer used and storage behavior remains covered.

Written by the indexing model from the issue text.