Python code modernization, 2/n (#1156)

* 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

* Reformat.

plugins/plugin_utils/_socket_handler.py

@@ -5,7 +5,7 @@
 # Note that this module util is **PRIVATE** to the collection. It can have breaking changes at any time.
 # Do not use this from other collections or standalone plugins/modules!
 
-from __future__ import absolute_import, division, print_function
+from __future__ import annotations
 
 
 __metaclass__ = type