Add redbot-setup restore cli command for restoring instance from backup

[Jackenmen]

Type

• Bugfix
• Enhancement
• New feature

Description of the changes

Fixes #2947

I added progress bars to indicate to the user that the command does something but they're surely not the most accurate progress bars - progress bar for (un)packing archives are based on file amount, not on file size and progress bar for downloading repos is based on repo amount. I'm open to improving it but I think it still serves its purpose even if it's not very linear.

Note:

Restoring cogs is still far from perfect as it requires running [p]cog update after the offline restoring process so that the previously installed cogs get reinstalled (it's totally possible to reinstall cogs offline but it would require rewriting more than I currently have time for).

I decided to finish it up anyway and we can decide later in the org whether we want to freeze this until appropriate rewriting is done or if the feature is good enough to ship it before that's done.

Other minor fixes/enhancements:

• backup can now have a version of its own if we would need to change something about its format later
• passing wrong data path to redbot-setup and redbot --edit no longer stops whole process and instead asks for the path again
• passing an already used name for instance and deciding not to replace it no longer stops whole process and instead asks for the instance name again
• redbot-setup delete no longer tries to connect to database if user doesn't want to delete instance's data
• --debug is now a flag in redbot-setup to be consistent with redbot

note to self: rebase push was: 2c9f3d0...5a9a55d

[Jackenmen]

This PR is ready for review. Or at least as ready as it can be - restoring cogs is still far from perfect as it requires running [p]cog update after the offline restoring process so that the previously installed cogs get reinstalled (it's totally possible to reinstall cogs offline but it would require rewriting more than I currently have time for).

I decided to finish it up anyway and we can decide later in the org whether we want to freeze this until appropriate rewriting is done or if the feature is good enough to ship it before that's done.