Show progress of upload to remote builder

[Thra11]

Is your feature request related to a problem? Please describe.

When downloading data, the new (nix 2) nix UI shows the download progress as [downloaded/total]. However, when uploading data to a remote builder, the progress isn't shown, making it difficult to tell how much longer it might take, or whether it's stalled.

Describe the solution you'd like

It would be nice if it showed the upload progress when uploading data to a remote builder (although the status line is already too long, so I'm not sure how it would fit).

[stale]

I marked this as stale due to inactivity. → More info