Showing progress bar when running `verdi storage maintain`.

[unkcpz]

I am running the command on the repository that occupying >200GB. After checking with @giovannipizzi, he estimate it will cost ~8 h. I was panic not see anything is progress and my disk space keeps going lower.

[giovannipizzi]

I also discussed this with @khsrali @agoscinski @GeigerJ2 at some point, I habe the feeling there might even be some work already done in this direction? Just pinging them to avoid duplication of work. Note that this, I think, requires changes in disk objectstore, so should first be implemented there, and then called properly in AiiDA

[giovannipizzi]

Note also #5485

[khsrali]

yes, I opened a PR in disk-objectstore sometime ago, @unkcpz would be great if you can review it.