Add validation for packages secret

Customers sometimes input invalid credentials when creating the aws-secret used to pull packages. We can add to the troubleshooting docs on some more symptoms like the 401 Unauthorized error in the package containers as well as add a validation the customers can run from the CLI to ensure their secret is healthy/valid.

No files, tests, or entry points are named. Start by locating the troubleshooting documentation and the CLI path for the Kubernetes aws-secret, then confirm the intended symptoms and validation behavior with maintainers. Done means the docs address 401 Unauthorized package-container errors and the CLI can report whether the secret is healthy and valid.

Written by the indexing model from the issue text.