archiver: Create a subcommmand debug for all debug-* commands
archiver: Create a subcommmand debug for all debug-* commands

The debug commands all should subcommands of a common debug command.

This commit adds this command but keeps the old command names for 1.0.x.
The plan is to remove them in 1.1.0.

RonnyPfannschmidt/borg,edgewood/borg,edgimar/borg,raxenak/borg,raxenak/borg,edgewood/borg,raxenak/borg,RonnyPfannschmidt/borg,RonnyPfannschmidt/borg,RonnyPfannschmidt/borg,edgimar/borg,RonnyPfannschmidt/borg,edgewood/borg,raxenak/borg,edgewood/borg,edgimar/borg,edgimar/borg