Test till python 3.11

As per the current release tested runtime, we
need to test python 3.8 to python 3.11. Using the
generic python testing template which run py3.8 and py3.11
tests. Also, updating the same in python classifier in setup.cfg

Also, removing the tox based

Change-Id: Ieaf55c60c2851f3e9282590241696053f21eb4d3

.zuul.yaml

@@ -2,7 +2,7 @@
     queue: sahara
     templates:
       - publish-openstack-docs-pti
-      - openstack-python3-ussuri-jobs
+      - openstack-python3-jobs
       - release-notes-jobs-python3
     check:
       jobs:
@@ -28,9 +28,9 @@
             voting: false
         - sahara-tests-scenario-stein:
             voting: false
-        - openstack-tox-py36:
+        - openstack-tox-py38:
             voting: false
-        - openstack-tox-py37:
+        - openstack-tox-py311:
             voting: false            
     gate:
       jobs:
@@ -42,10 +42,6 @@
             voting: false
         - sahara-tests-tempest-v2:
             voting: false
-        - openstack-tox-py36:
-            voting: false
-        - openstack-tox-py37:
-            voting: false
     experimental:
       jobs:
         - sahara-tests-scenario-multinode-spark