Flake, flake-part+easy-host, remove unused inputs

IF YOU ARE NOT ME: I would not use this configuration. In the past I
would feel confident telling you to drop in your own host and be off to
the races, but right now users are in a state which required hard coding
some of my nominal preferences. Read on for more specifics

Completely refactors the flake.nix part of the repo. This removes my
strange legacy code for directory-based hosts+users in favor of using
easy-host and flake-parts.

As a result of this some specialArgs were lost, namely the list of users
and the username being passed. I think this is the right way to go in
the short term, but it has lead to some hardcoded values. Namely "pan"
is created as a user regardless of configuration

In tandem with this is the deprecation of some modules which had inputs
in flake which I wasn't using. I'm sure there is a better way to do
this, but I didn't like downloading and caching them every time when I
knew I wasn't using them.

I'm currently very unhappy with the users part of this change, but that
wasn't the goal of this branch. I will revisit in a larger commit.

users/badtz@juri/user.nix

@@ -0,0 +1,10 @@
+{ config, pkgs, ... }:
+
+{
+  fish.enable = true;
+  git = {
+    enable = true;
+    username = "Badtz";
+    email = "may@badtz.dev";
+  };
+}