Add redbot-setup restore cli command

[Jackenmen]

Description of the changes

Fixes #2947, depends on #6696, supersedes #3681

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.

Backup can now have a version of its own in case we need to change something about its format later.

Docs: https://red-discordbot--6709.org.readthedocs.build/en/6709/backup_red.html

Have the changes in this PR been tested?

Yes

[EternalllZM]

In regards to the docs on this, the current backup and restore page mentions (the possible need of) fixing permissions on Linux with the sudo chown -R <user>:<user> ~/.local command, that is removed in this PR.

data_path handles the restore location, would it be worth adding a check for file access? How would that be handled on a Windows to Linux or vise versa restore? Regardless, I think the command should remain in the backup/restore process docs just in case.

[Jackenmen]

In regards to the docs on this, the current backup and restore page mentions (the possible need of) fixing permissions on Linux with the sudo chown -R <user>:<user> ~/.local command, that is removed in this PR.

There should be no need for this unless the user has a seriously broken system. That's not on us to help with, and users will definitely just try running this command if something breaks for them due to unrelated reasons.

data_path handles the restore location, would it be worth adding a check for file access?

Yes, I missed that earlier and have just noticed in testing that we are, in fact, not checking whether the path is accessible at any point. I just fixed that.

How would that be handled on a Windows to Linux or vise versa restore

The updated code should make it so this fails on the is_absolute() call.

[Jackenmen]

Okay, I added support for non-interactive use, and this is now (again) ready for review. Please note, however, that as described in the description, this PR depends on #6696 to work correctly, and the changeset from that PR is not included in this PR's branch.

[Jackenmen]

I've made a slight change to metadata stored in the backup file - instead of a backup.version file storing just the version number, there's now a backup_details.json file with one backup_version key. While there was nothing stopping future versions of the backup format from storing additional metadata files, I figured it would be simpler if one could just use the same file for more purposes in the future.
Notably, I'm hoping this command could, in the future, have flags for making copies of installed cogs and installed repos, and the metadata would then have additional keys that tell you if such flags were used for the backup.
Here's an example of how such a change to the metadata would look in practice: Jackenmen@3fb4816

Another small change is the addition of dereference=True parameter to tarfile.open() to ensure we backup the actual files rather than symlinks, if any are present in the data dir.