[Dev UI] Render multiple candidates for image models

[MichaelDoyle]

Note: there is a proposal to remove multiple candidates from the API/model abstraction. In that case, we can still have the UI provide a selection for # of candidates, and make parallel calls for each request image, and display in a grid.

[chrisraygill]

I think @mbleigh was considering getting rid of multiple candidates in favor of making multiple calls in parallel.

[MichaelDoyle]

It's true :) I wrote that in the description. From a UX perspective, we might still want to do it. BUT, if not. Let's close this out. Let me know.

[mbleigh]

+1 to both getting rid of candidates generally and still supporting multiple generations for image models specifically. :)