Media modal improvement for new uploads

[jeffpaul]

Is your enhancement related to a problem? Please describe. Following on from #295, we'll want to investigate how to further improve the generate/regenerate/rescan buttons in the media modal when editing a post so you no longer have to click away and then back to have the buttons work.

Describe the solution you'd like

Designs

Describe alternatives you've considered

Additional context Original, larger focus issue: #292.

[dkotter]

Specific context is here: https://github.com/10up/classifai/pull/295#issuecomment-884962243