[swift] Transition Xena to EM

This transition the stable/xena branch to extended maintenance.
Changes for bugfixes and things the team deems important are
still encouraged, but there will no longer be official releases
off of the branch after the transition.

Please +1 if the team is ready for us to proceed with this
transition, or -1 if there are any final backports currently in
flight that we should wait for. For the latter case, please
update the patch with the new commit hash after doing a final
release to get those changes out so we know to proceed with the
transition.

The transition deadline is April 20th, 2023.

Change-Id: I58a08512db162b05a1f86fb70078d825cc946ff6

deliverables/xena/python-swiftclient.yaml

@@ -11,6 +11,10 @@ releases:
     projects:
       - repo: openstack/python-swiftclient
         hash: 38c435f88833869c0d0121a6e7e2c16ac1a7e3be
+  - version: xena-em
+    projects:
+      - repo: openstack/python-swiftclient
+        hash: 38c435f88833869c0d0121a6e7e2c16ac1a7e3be
 branches:
   - name: stable/xena
     location: 3.12.0

deliverables/xena/swift.yaml

@@ -14,6 +14,10 @@ releases:
     projects:
       - repo: openstack/swift
         hash: b1916f81e2a598b41ab7281259c78715d7e46955
+  - version: xena-em
+    projects:
+      - repo: openstack/swift
+        hash: b1916f81e2a598b41ab7281259c78715d7e46955
 branches:
   - name: stable/xena
     location: 2.28.0