nix: refactor module structure and flake output (#1014)

- The program module is now called dank-material-shell
- The homeModules structure is flattened

distro/nix/dms-rename.nix

@@ -0,0 +1,15 @@
+{ lib, ... }:
+{
+  imports = [
+    (lib.mkRenamedOptionModule
+      [
+        "programs"
+        "dankMaterialShell"
+      ]
+      [
+        "programs"
+        "dank-material-shell"
+      ]
+    )
+  ];
+}