This converts from the old manually defined users in flake.nix to a
dynamically defined users based on the directory structure. This is the
same as ba5fd48 but for users instead of hosts.
Previously the home-manager and nixos sections of my config had been
separated into different branches on the same repository. This commit
merges the home-manager modules into the directory, and convert the
"systems" that used to be on each branch into hosts and users.
The goal of this change is to make it easier to see the hosts and users
paradigm, as well as limit the number of locations the git repository is
installed. Additionally, having different branches tracking different
changes was silly for a git repository.
