[Tempest] Tag train-last

Train branch is in Extended Maintenance now[1]. Tempest and
tempest plugins are branchless which means master version of
Tempest and its plugins is used to test the supported stable
branches.

Once any stable branch is moved to EM state then, Tempest and
its plugins compatible tag needs to be released so that we can
keep testing the EM stable branches with that tag once master
Tempest and its plugins are not compatible[2].

Documentation this tag
- https://docs.openstack.org/project-team-guide/stable-branches.html#extended-maintenance

More detail on compatible version policy for Tempest and its
plugins is here
- https://docs.openstack.org/tempest/latest/tempest_and_plugins_compatible_version_policy.html

[1] https://releases.openstack.org/train/index.html
[2] https://docs.openstack.org/tempest/latest/stable_branch_support_policy.html

Change-Id: I5e3bec00a75a3213e0aab810a6e797f3e34d5d08

deliverables/train/tempest.yaml

@@ -19,6 +19,10 @@ releases:
       - repo: openstack/tempest
         hash: c93345233e06c173a65a3edcb769c4220386b3bd
     version: 22.1.0
+  - version: train-last
+    projects:
+      - repo: openstack/tempest
+        hash: 2eb82f1cbc2bd1e189e33ee65a5beb33aff9d1f5
 repository-settings:
   openstack/tempest:
     pypi-name: Tempest

deliverables/xena/tempest.yaml

@@ -8,3 +8,8 @@ stable-branch-type: none
 repository-settings:
   openstack/tempest:
     pypi-name: Tempest
+releases:
+  - projects:
+      - repo: openstack/tempest
+        hash: 2eb82f1cbc2bd1e189e33ee65a5beb33aff9d1f5
+    version: 28.0.0