refactor(schema): simplify dict normalization and schema checks

roles/global_defaults/defaults/main.yml

@@ -82,3 +82,12 @@ system_defaults:
       sudo: true
     chroot:
       tool: "arch-chroot" # arch-chroot|chroot|systemd-nspawn
+
+system_disk_defaults:
+  size: 0
+  device: ""
+  mount:
+    path: ""
+    fstype: ""
+    label: ""
+    opts: "defaults"