vars/keygen: fix + cleanup tests

- generate keys in ./sops instead of ./sops/vars for now
- don't initialize all flakes with sops keys, only generate when needed
- use the new 'clan vars keygen' in tests

pkgs/clan-cli/tests/test_vms_cli.py

@@ -82,7 +82,6 @@ def test_vm_persistence(
         temporary_home,
         flake_template=CLAN_CORE / "templates" / "minimal",
         machine_configs=config,
-        monkeypatch=monkeypatch,
     )
 
     monkeypatch.chdir(flake.path)