build: add determinate nix support for darwin

- Add determinateSystems/determinate flake input
- Include determinate darwin modules in configuration
- Disable legacy nix module configuration
- Remove modules/darwin/nix/default.nix
- Add mac-va-mbp-work system using determinate nix

systems/aarch64-darwin/mac-va-mbp-work/default.nix

@@ -0,0 +1,11 @@
+{
+  system.stateVersion = 6;
+
+  # System Config
+  determinateNix = {
+    enable = true;
+    nixosVmBasedLinuxBuilder.enable = true;
+  };
+
+  reichard = { };
+}