Use sas for agent log download

[tevoinea]

Summary of the Pull Request

What is this about?
This allows the client to use a SAS URL generated by the service as the authentication mechanism to download a container from a storage account.

It follows this pattern: https://docs.microsoft.com/en-us/azure/storage/common/storage-sas-overview#when-to-use-a-shared-access-signature

PR Checklist

• Applies to work item: #xxx
• CLA signed. If not, go over here and sign the CLI.
• Tests added/passed
• Requires documentation to be updated
• I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #xxx

Info on Pull Request

What does this include?

1. Download containers via SAS URL
2. Some small dev container quality of life improvements

Validation Steps Performed

How does someone test & validate?

1. Run onefuzz debug logs get --job_id {job_id}
2. Check the files were still downloaded