[Windows] Security model for files permissions - STEP 1 (#6893)

This PR is the first part of #6497 to ease the integration, following the new plan propose by @bmw here: #6497 (comment)

This step 1 refactor existing certbot.compat module into certbot.compat.misc, without any logic changed. Package certbot.compat will host the new modules that constitute the security model for Windows.

* Create the certbot.compat package. Move logic in certbot.compat.misc

* Add doc

* Fix lint

* Correct mypy

* Update client.py

certbot/log.py

@@ -13,6 +13,7 @@ and properly flushed before program exit.
 
 """
 from __future__ import print_function
+
 import functools
 import logging
 import logging.handlers
@@ -23,10 +24,10 @@ import traceback
 
 from acme import messages
 
-from certbot import compat
 from certbot import constants
 from certbot import errors
 from certbot import util
+from certbot.compat import misc
 
 # Logging format
 CLI_FMT = "%(message)s"
@@ -134,7 +135,7 @@ def setup_log_file_handler(config, logfile, fmt):
     # TODO: logs might contain sensitive data such as contents of the
     # private key! #525
     util.set_up_core_dir(
-        config.logs_dir, 0o700, compat.os_geteuid(), config.strict_permissions)
+        config.logs_dir, 0o700, misc.os_geteuid(), config.strict_permissions)
     log_file_path = os.path.join(config.logs_dir, logfile)
     try:
         handler = logging.handlers.RotatingFileHandler(