Add borg compact command support

This addresses a novelty of borg 1.2 which now includes a compact command. See #11351

Note that I didn't try to make it smart. One may set compact to yes explicitely. No attempt at detect whether remote will support it.

Also, didn't activate it by default, as upstream doesn't seem to recommend it: https://borgbackup.readthedocs.io/en/stable/usage/notes.html#separate-compaction

mentioned in issue #11340 (closed)

I am sorry about the my response time. I have done it another way. I check the borg version, and compact if >1.2. But I have other changes that need work to be commited upstream. It's bad I'm sorry.

I hope to find time in the next days/weeks to update this handler.

@maethor any news on that front ?

Thanks in advance

Closed by commit b37edd26

closed