Fix __future__ imports, __metaclass__ = type, and remove explicit UTF-8 encoding statement for Python files (#10886)

* Adjust all __future__ imports:

for i in $(grep -REl "__future__.*absolute_import" plugins/ tests/); do
  sed -e 's/from __future__ import .*/from __future__ import annotations/g' -i $i;
done

* Remove all UTF-8 encoding specifications for Python source files:

for i in $(grep -REl '[-][*]- coding: utf-8 -[*]-' plugins/ tests/); do
  sed -e '/^# -\*- coding: utf-8 -\*-/d' -i $i;
done

* Remove __metaclass__ = type:

for i in $(grep -REl '__metaclass__ = type' plugins/ tests/); do
  sed -e '/^__metaclass__ = type/d' -i $i;
done

plugins/module_utils/univention_umc.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 
 # This code is part of Ansible, but is an independent component.
 # This particular file snippet, and this file snippet only, is BSD licensed.
@@ -12,8 +11,7 @@
 # Simplified BSD License (see LICENSES/BSD-2-Clause.txt or https://opensource.org/licenses/BSD-2-Clause)
 # SPDX-License-Identifier: BSD-2-Clause
 
-from __future__ import (absolute_import, division, print_function)
-__metaclass__ = type
+from __future__ import annotations
 
 
 """Univention Corporate Server (UCS) access module.