Deprecate bifrost

It has long been sort of an abomination of the container world,
let's use this deprecation notice as a motivation to work out
a kolla-ansible mechanism utilising regular ironic container
images to deploy standalone ironic.

Change-Id: I6b4e6edc110eebb524396138d24b873cb4ea6726

Author: mnasiadka

releasenotes/notes/deprecate-bifrost-dd93b6d8eb04cac6.yaml

@@ -0,0 +1,6 @@
+---
+deprecations:
+  - |
+    Building ``bifrost-deploy`` container image has been deprecated, in favor
+    of a new ironic standalone deployment using ``ironic`` container images
+    that will be implemented in ``kolla-ansible`` in the next cycles.