Add no-home-volume layout for LVM installation

[recolic]

PR Description:

This PR allows creating LVM installation without separate home volume.

Tests and Checks

• I have tested the code!
  

Test: default layout works

Test: no-home layout works

Test: default layout + btrfs subvol works

Test: no-home layout + btrfs subvol no effect (no-home is controlled inside btrfs subvol)

[recolic]

I think get_default_btrfs_subvols() might also need a HomeVolume=True/False option?

[svartkanin]

The description on the top of the configuration still reads
Configuration: Default layout (root volume + seperate home volume) even though no home was selected.

The saved configuration also doesn't seem to store the correct value

...
        "lvm_config": {
            "config_type": "default",
            "vol_groups": [
                {
...

I'd also rename the options to be

• Default layout
• Root only