rewrite the download button/link code

[williamstein]

Possibly rewrite the code from #984. Maybe we shouldn't construct a separate URL, download function, etc., for every single file in the listing while making the listing. That might (??) be a waste of time, and not necessary (what if the file listing has 250 entries in)? When Jonathan, Nicholas and I wrote the file listing code we spent days optimizing it to be super fast for potentially large numbers of files, even when doing realtime searches. The download link code potentially adds overhead. Also calling an action in a render method is dangerous, which caused #1011

A better way is to just have one single clickable function which all of the file listing things call. Or something. I don't know. But we can maybe do better.

I remember making mistakes like this and fixing them long ago with the first few iterations of file listings.

[williamstein]

Related note:

The code

href_download = @props.actions.download_href(@fullpath())

isn't good since actions aren't supposed to return anything.