Drop python3.6/3.7 support in testing runtime

In Zed cycle testing runtime, we are targetting to drop the
python 3.6/3.7 support, project started adding python 3.8 as minimum,

example nova:
- https://github.com/openstack/nova/blob/56b5aed08c6a3ed81b78dc216f0165ebfe3c3350/setup.cfg#L13

Also moving zuul jobs to Zed.
Also indicate that we support py3.9

Change-Id: Ifb6188b4e623d40bcadb3c92462024f80616291d

move victoria's zuul jobs to zed

Change-Id: I0200db8add157d28a0bc0859ea126b2e4711f75e

.zuul.yaml

@@ -2,7 +2,7 @@
     templates:
       - check-requirements
       - lib-forward-testing-python3
-      - openstack-python3-victoria-jobs
+      - openstack-python3-zed-jobs
       - periodic-stable-jobs
       - publish-openstack-docs-pti
       - release-notes-jobs-python3

setup.cfg

@@ -6,7 +6,7 @@ summary = Oslo Metrics API
 description_file =
     README.rst
 home_page = https://opendev.org/openstack/oslo.metrics
-python_requires = >=3.6
+python_requires = >=3.8
 classifier =
     Environment :: OpenStack
     Intended Audience :: Developers
@@ -15,9 +15,8 @@ classifier =
     Operating System :: OS Independent
     Programming Language :: Python
     Programming Language :: Python :: 3
-    Programming Language :: Python :: 3.6
-    Programming Language :: Python :: 3.7
     Programming Language :: Python :: 3.8
+    Programming Language :: Python :: 3.9
     Programming Language :: Python :: 3 :: Only
     Programming Language :: Python :: Implementation :: CPython