Enhancement: add more status counters to `restic copy`

`restic copy` now produces more status counters in text format. The new counters
are the number of blobs to copy, their size on disk and the number of packfiles
used from the source repository. The additional statistics is only produced when
the `--verbose` option is specified.

https://github.com/restic/restic/issues/5175
https://github.com/restic/restic/pull/5319