[Tempest Plugins] Tag stein-last

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

Once 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 this tag once master
Tempest and its plugins are not compatible[2].

This tag will help for testing the stable/stein with single
compatible tag of Tempest and its plugins.

Tagging 'stein-last' as well as a new version also with same hash.
Documenting this new tag name here
- https://review.opendev.org/c/openstack/project-team-guide/+/769821

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/stein/index.html
[2] https://docs.openstack.org/tempest/latest/stable_branch_support_policy.html

Change-Id: I4f8aca952fae44a737cab10f56d2dac0648d4503

deliverables/stein/solum-tempest-plugin.yaml

@@ -12,3 +12,7 @@ releases:
     projects:
       - repo: openstack/solum-tempest-plugin
         hash: 900f4870a53bf28b42eaf44797202edd3740f9ae
+  - version: stein-last
+    projects:
+      - repo: openstack/solum-tempest-plugin
+        hash: 80e23bb97926308505bc0ac206974468b38efe4e

deliverables/wallaby/solum-tempest-plugin.yaml

@@ -8,3 +8,8 @@ repository-settings:
   openstack/solum-tempest-plugin: {}
 team: solum
 type: tempest-plugin
+releases:
+  - version: 2.2.0
+    projects:
+      - repo: openstack/solum-tempest-plugin
+        hash: 80e23bb97926308505bc0ac206974468b38efe4e