Deprecate Windows support

Unfortunately the Winstackers project has been retired because of no
maintainers[1][2], and OpenStack on Windows host is no longer
maintained.

[1] https://lists.openstack.org/pipermail/openstack-discuss/2022-November/031044.html
[2] https://review.opendev.org/c/openstack/governance/+/886880

Change-Id: I4ad06af023fb4812dc9c6a15a23c5e85ef6cce8d

oslo_log/_options.py

@@ -111,6 +111,8 @@ generic_log_opts = [
                      + _IGNORE_MESSAGE),
     cfg.BoolOpt('use_eventlog',
                 default=False,
+                deprecated_for_removal=True,
+                deprecated_reason='Windows support is no longer maintained.',
                 help='Log output to Windows Event Log.'),
     cfg.IntOpt('log_rotate_interval',
                default=1,

releasenotes/notes/deprecate-windows-support-75e6ac72310d5e72.yaml

@@ -0,0 +1,5 @@
+---
+deprecations:
+  - |
+    Windows support has been deprecated, because of the retiremenet of
+    the Winstackers project.