[Tempest] release 31.0.0 and tag ussuri-last, victoria-last

Ussuri and Victoria 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].

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

Releasing a new major version as tempest drop py3.6 and py3.7 support
also.

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

Change-Id: I3c1f1b7e7163c287ba7f502c446513db86eb7fc9

deliverables/ussuri/tempest.yaml

@@ -15,6 +15,10 @@ releases:
       - repo: openstack/tempest
         hash: c73e6b11dcc1fcd878ff62e353441a5c8c794c83
     version: 24.0.0
+  - version: ussuri-last
+    projects:
+      - repo: openstack/tempest
+        hash: abddb57fd1974c546a6228b4eb53c1d7bb69ab38
 repository-settings:
   openstack/tempest:
     pypi-name: Tempest

deliverables/victoria/tempest.yaml

@@ -17,3 +17,7 @@ releases:
     projects:
       - repo: openstack/tempest
         hash: 94a76091f616a4e4a46534b82d4974534d197643
+  - version: victoria-last
+    projects:
+      - repo: openstack/tempest
+        hash: abddb57fd1974c546a6228b4eb53c1d7bb69ab38

deliverables/zed/tempest.yaml

@@ -5,6 +5,11 @@ release-model: cycle-with-intermediary
 team: Quality Assurance
 type: other
 stable-branch-type: none
+releases:
+  - projects:
+      - repo: openstack/tempest
+        hash: abddb57fd1974c546a6228b4eb53c1d7bb69ab38
+    version: 31.0.0
 repository-settings:
   openstack/tempest:
     pypi-name: Tempest