refactor: remove Machine.vars_generators() method

Replace all calls to machine.vars_generators() with direct calls to
Generator.generators_from_flake() to make the dependency more explicit
and remove unnecessary indirection.

This reduces coupling to the Machine class, making the codebase more
modular and easier to refactor in the future.

pkgs/clan-cli/clan_lib/machines/machines.py

@@ -21,7 +21,7 @@ from clan_lib.ssh.remote import Remote
 log = logging.getLogger(__name__)
 
 if TYPE_CHECKING:
-    from clan_cli.vars.generate import Generator
+    pass
 
 
 @dataclass(frozen=True)
@@ -118,11 +118,6 @@ class Machine:
             return services
         return {}
 
-    def vars_generators(self) -> list["Generator"]:
-        from clan_cli.vars.generate import Generator
-
-        return Generator.generators_from_flake(self.name, self.flake, self)
-
     @property
     def secrets_upload_directory(self) -> str:
         return self.select("config.clan.core.facts.secretUploadDirectory")