Update the subvolume menu - fix for #1278

[svartkanin]

Subvolume changes

Addresses issues

• Fixes Re-write the subvolume menu  #1278
• Fixes AttributeError: 'str' object has no attribute 'update' when adding subvolumes #1151
• Fixes On the BTRFS subvolume menu, show the default structure #1131
• Fix small bug when returning from harddrive selection; when not selecting antying with Esc it would blow up
• Fix small bug when going into a submenu selection (e.g. user creation menu) and there was no data present the selection > would be set on an empty line

Changes

Introduce a new dataclass for Subvolumes

When storing subvolume information in the partition['btrfs']['subvolume'] dictionary container we no longer have to deal with native types but now have the class Subvolume that encapsulates the relevant information. This should alleviate possible bugs in the future.
With this change the relevant code parts have been updated as well (hopefully without any mistakes). As this change is also part of the configuration that can be saved/loaded that one also has been updated.

New configuration schema

The old configuration schema for disk layouts looked like this

"btrfs": {
                    "subvolumes": {
                        "@": "/",
                        "@.snapshots": "/.snapshots",
                        "@home": "/home",
                        "@log": "/var/log",
                        "@pkg": "/var/cache/pacman/pkg"
                    }
                },

this has now migrated to

 "btrfs": {
                    "subvolumes": [
                        {
                            "compress": false,
                            "mountpoint": "/",
                            "name": "@",
                            "nodatacow": false
                        },
                        {
                            "compress": false,
                            "mountpoint": "/home",
                            "name": "@home",
                            "nodatacow": false
                        },
                        {
                            "compress": false,
                            "mountpoint": "/var/log",
                            "name": "@log",
                            "nodatacow": false
                        },
                        {
                            "compress": false,
                            "mountpoint": "/var/cache/pacman/pkg",
                            "name": "@pkg",
                            "nodatacow": false
                        },
                        {
                            "compress": false,
                            "mountpoint": "/.snapshots",
                            "name": "@.snapshots",
                            "nodatacow": false
                        }
                    ]
                },

@Torxed This is backwards compatible similar to the user credential changes

New Subvolume menu

Future changes

• Pass through current configuration to the partitioning menu properly so it actually can be edited
• As mentioned by @dylanmtaylor Re-write the subvolume menu  #1278 (comment) the table view is quite poor atm and I'll address that in a followup PR

@Torxed I know this is a big one, but I was hoping to get this out now so there's enough time to thoroughly test it before the next release :)

[svartkanin]

Also fixes #1305

[Torxed]

Awesome work. I don't mind them being huge hehe.
But I'm on vacation and a bit on the run, could I bother you with fixing the merge conflict with users.py? After that I can merge it!

[svartkanin]

@Torxed fixed the conflicts!
Ahh yeah that's right Sweden is essentially shut down now for 2 months ;) happy holidays!

[Torxed]

@Torxed fixed the conflicts! Ahh yeah that's right Sweden is essentially shut down now for 2 months ;) happy holidays!

Haha, thanks! We sure are! Industrial holiday ftw, even if you're not in the industrial field. ^^