Feature: Display outputs in the Backstage entity card

[clareliguori]

We had a request to display Proton outputs in the Backstage entity card. For example, displaying the outputs of a pipeline resource, outputs of a service instance resource, and/or outputs of an environment resource. This request probably needs some further thought about where we draw the line of displaying everything in the Backstage UI vs providing surface-level information and a link to view more detailed information in the Proton console.