CLI: improve UX on attestation downloading #31

When an user retrieves the information of an attestation, i.e chainloop wf run describe --id [ID], the prompt takes up to a couple of seconds due to the fact that in the backend, the attestation is retrieved from an OCI registry.

This makes the user experience sub-optimal, we should probably tell the user that the system is working and we are waiting for the attestation.

We have different feedback options

• 1. text based: Something like "retrieving information..."
• 2. leverage current library we are already using for download tracking https://github.com/jedib0t/go-pretty
• 3. or alternatively implement or use a simple spinner library https://github.com/briandowns/spinner

I'd personally check if 2 is a good fit since we already use it.