Include list of device-mapper devices in debug output

I’m having a hard time with some bug reports regarding VeraCrypt volumes. It might help if the whisperback reports would not only include mounted volumes, but also unmounted but unlocked ones.

A useful list of unlocked devices can be retrieved with this command:

dmsetup ls --tree -o blkdevname,uuid,active,open,rw,notrunc

The list of loop devices could also be helpful:

losetup -l -O NAME,BACK-FILE,AUTOCLEAR,RO,PARTSCAN,SIZELIMIT,OFFSET

Feature Branch: feature/15966-dm-and-loop-debug-output

Parent Task: #14477 (closed)

Original created by @segfault on 15966 (Redmine)