amount of backup data in human readable size (MB/GB/TB)

[slu-010101]

Hi,

it would be nice to make this info more human readable:

[2024-04-07 12:50:09] INFO root disk - backup [vda]: Got 7183 extents to backup.
[2024-04-07 12:50:09] INFO root disk - backup [vda]: 2147483648000 bytes disk size
[2024-04-07 12:50:09] INFO root disk - backup [vda]: 1351024640 bytes of data extents to backup

Or some statistic after the successful backup to see something is curious (ransomware,...).

[slu-010101]

There is an issue about this:
#173