Add a progress bar on scan command

added activity::Implementation roadmap_import labels

moved from swh/meta#4843 (moved)

do we consider the counters currently available as a suitable solution?

FTR it will show and update the number of scanned objects and the number of objects compared with the archive, ending with something like:

1769 local objects scanned
1706/1706 objects compared with the Software Heritage archive

(these numbers are updated in real time during the scanning phase)

Let's say yes

closed