refactor: split common/nixos.nix and -/home.nix

Split these big files into modular files that
are easier to share and read on their own.

profiles/sandbox/disk-config.nix

@@ -0,0 +1,56 @@
+# Example to create a bios compatible gpt partition
+{ lib, ... }:
+{
+  disko.devices = {
+    disk.disk1 = {
+      device = lib.mkDefault "/dev/sda";
+      type = "disk";
+      content = {
+        type = "gpt";
+        partitions = {
+          boot = {
+            name = "boot";
+            size = "1M";
+            type = "EF02";
+          };
+          esp = {
+            name = "ESP";
+            size = "500M";
+            type = "EF00";
+            content = {
+              type = "filesystem";
+              format = "vfat";
+              mountpoint = "/boot";
+            };
+          };
+          root = {
+            name = "root";
+            size = "100%";
+            content = {
+              type = "lvm_pv";
+              vg = "pool";
+            };
+          };
+        };
+      };
+    };
+    lvm_vg = {
+      pool = {
+        type = "lvm_vg";
+        lvs = {
+          root = {
+            size = "100%FREE";
+            content = {
+              type = "filesystem";
+              format = "ext4";
+              mountpoint = "/";
+              mountOptions = [
+                "defaults"
+              ];
+            };
+          };
+        };
+      };
+    };
+  };
+}