feat: Update hardware configuration and extract disk setup

This commit refactors the hardware configuration in the SGX attic. A new file named `disko.nix` has been added which houses the disk setup previously located on `hardware-configuration.nix`. Additionally, some parameters in `default.nix` have been updated and unneeded configuration settings have been removed.

systems/x86_64-linux/sgx-attic/disko.nix

@@ -0,0 +1,41 @@
+# USAGE in your configuration.nix.
+# Update devices to match your hardware.
+# {
+#  imports = [ ./disko-config.nix ];
+#  disko.devices.disk.main.device = "/dev/sda";
+# }
+{
+  config.disko.devices = {
+    disk = {
+      main = {
+        type = "disk";
+        content = {
+          type = "gpt";
+          partitions = {
+            boot = {
+              size = "1M";
+              type = "EF02"; # for grub MBR
+            };
+            ESP = {
+              size = "1G";
+              type = "EF00";
+              content = {
+                type = "filesystem";
+                format = "vfat";
+                mountpoint = "/boot";
+              };
+            };
+            root = {
+              size = "100%";
+              content = {
+                type = "filesystem";
+                format = "ext4";
+                mountpoint = "/";
+              };
+            };
+          };
+        };
+      };
+    };
+  };
+}