clan-cli: machines delete: delete the machine's vars and secrets

When a machine is deleted with `clan machines delete`, remove its
vars and legacy secrets, and update any secrets that reference the
machine's key.

This command is a superset of `clan secrets machine delete`, and I am
wondering if we could remove the `clan secrets machine` subcommand,
unless there is an use case for having a machine defined without its
key, and any secrets/vars?

Note:

- This deletes the `ListSecretsOptions` dataclass, as it did not seem to
  bring any value, especially since `list_secrets` was receiving its
  individual members instead of the whole dataclass. We can always bring
  it back if complexity grows to demand it.

pkgs/clan-cli/clan_cli/completions.py

@@ -208,16 +208,11 @@ def complete_secrets(
     Provides completion functionality for clan secrets
     """
     from .clan_uri import Flake
-    from .secrets.secrets import ListSecretsOptions, list_secrets
+    from .secrets.secrets import list_secrets
 
     flake = clan_dir_result if (clan_dir_result := clan_dir(None)) is not None else "."
 
-    options = ListSecretsOptions(
-        flake=Flake(flake),
-        pattern=None,
-    )
-
-    secrets = list_secrets(options.flake.path, options.pattern)
+    secrets = list_secrets(Flake(flake).path)
 
     secrets_dict = dict.fromkeys(secrets, "secret")
     return secrets_dict