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/modules/mssql_db.py

@@ -1,13 +1,11 @@
 #!/usr/bin/python
-# -*- coding: utf-8 -*-
 
 # Copyright (c) 2014, Vedit Firat Arig <firatarig@gmail.com>
 # Outline and parts are reused from Mark Theunissen's mysql_db module
 # GNU General Public License v3.0+ (see LICENSES/GPL-3.0-or-later.txt or https://www.gnu.org/licenses/gpl-3.0.txt)
 # SPDX-License-Identifier: GPL-3.0-or-later
 
-from __future__ import absolute_import, division, print_function
-__metaclass__ = type
+from __future__ import annotations
 
 
 DOCUMENTATION = r"""