Remove dependency on six (#8650)

Fixes https://github.com/certbot/certbot/issues/8494.

I left the `six` dependency pinned in `tests/letstest/requirements.txt` and `tools/oldest_constraints.txt` because `six` is still a transitive dependency with our current pinnings.

The extra moving around of imports is due to me using `isort` to help me keep dependencies in sorted order after replacing imports of `six`.

* remove some six usage in acme

* remove six from acme

* remove six.add_metaclass usage

* fix six.moves.zip

* fix six.moves.builtins.open

* six.moves server fixes

* 's/six\.moves\.range/range/g'

* stop using six.moves.xrange

* fix urllib imports

* s/six\.binary_type/bytes/g

* s/six\.string_types/str/g

* 's/six\.text_type/str/g'

* fix six.iteritems usage

* fix itervalues usage

* switch from six.StringIO to io.StringIO

* remove six imports

* misc fixes

* stop using six.reload_module

* no six.PY2

* rip out six

* keep six pinned in oldest constraints

* fix log_test.py

* update changelog

certbot-apache/certbot_apache/_internal/parser.py

@@ -5,7 +5,6 @@ import logging
 import re
 import sys
 
-import six
 
 from acme.magic_typing import Dict
 from acme.magic_typing import List
@@ -275,7 +274,7 @@ class ApacheParser(object):
         while len(mods) != prev_size:
             prev_size = len(mods)
 
-            for match_name, match_filename in six.moves.zip(
+            for match_name, match_filename in zip(
                     iterator, iterator):
                 mod_name = self.get_arg(match_name)
                 mod_filename = self.get_arg(match_filename)