Avoid `eprintln!` for progress bar messages in CI

[szokeasaurusrex]

When progress bars are disabled, which is by default in CI, we log any messages that usually would go to the progress bar straight to stderr instead. In some CI configurations, however, any output to stderr is treated as an error. To avoid this for purely informational logs, we should instead use log::info!. As this is below our default log warning, the messages will be suppressed by default.

[linear]

CLI-244

[KostasVsNT]

+1 to this. We would like to catch any actual errors in the future, and surface them, including in the (unlikely?) scenario where the exit code would be 0, but we can't right now, as everything is printed via stderr:

Command line:

debug-files upload --org ... --project ... --no-zips --no-sources --log-level info <blah>

Thanks.