chore: migrate gsutil usage to gcloud storage

[gurusai-voleti]

Automated: Migrate {target_path} from gsutil to gcloud storage

This CL is part of the on going effort to migrate from the legacy gsutil tool to the new and improved gcloud storage command-line interface.
gcloud storage is the recommended and modern tool for interacting with Google Cloud Storage, offering better performance, unified authentication, and a more consistent command structure with other gcloud components. 🚀

⚠️ Action Required: Please Review and Test Carefully

While we have based the automation on the migration guide, every use case is unique.
It is crucial that you thoroughly test these changes in environments appropriate to your use-case before merging.
Be aware of potential differences between gsutil and gcloud storage that could impact your workflows.
For instance, the structure of command output may have changed, requiring updates to any scripts that parse it. Similarly, command behavior can differ subtly; the gcloud storage rsync command has a different file deletion logic than gsutil rsync, which could lead to unintended file deletions.

Our migration guides can help guide you through a list of mappings and some notable differences between the two tools.

Standard presubmit tests are run as part of this CL's workflow. If you need to target an additional test workflow or require assistance with testing, please let us know.

Please verify that all your Cloud Storage operations continue to work as expected to avoid any potential disruptions in production.

Automation Details

This change was generated automatically by an agent that targets users of gsutil.
The transformations applied are based on the gsutil to gcloud storage migration guide (external guide).

Support and Collaboration

The GCS CLI team is here to help! If you encounter any issues, have a complex use case that this automated change doesn't cover, or face any other blockers, please don't hesitate to reach out.
We are happy to work with you to test and adjust these changes as needed.

Contact: gcs-cli-hyd@google.com

We appreciate your partnership in this important migration effort!

#gsutil-migration

[gurusai-voleti]

Hi @smarthg-gi, Can we get your review on this PR? Thanks!

[gemini-code-assist]

Code Review

This pull request migrates GCS operations in import-automation/executor/run_import.sh from gsutil to gcloud storage. The review feedback highlights two important improvements: appending a trailing slash to the directory path in gcloud storage ls to prevent incorrect prefix matching, and redirecting standard error to /dev/null when reading staging_version.txt to avoid noisy logs if the file is missing.