Update 'openstack-python3-charm-jobs' to latest Python

Modify 'openstack-python3-charm-jobs' so that it mimics the behavior of
the recently introduced 'openstack-python3-jobs' template, allowing us
to add a (non-voting) 3.10 job, and remove the 3.5, 3.6 and 3.9 jobs.

Originally by Stephen Finucane <stephenfin@redhat.com>

Change-Id: Ic6b29e0f70b71de25d6b1bee306a2608e59451c5

zuul.d/project-templates.yaml

@@ -500,44 +500,6 @@
             required-projects:
               - openstack/neutron
 
-- project-template:
-    name: openstack-python3-charm-jobs
-    description: |
-      Runs unit tests for an OpenStack Charm project under the CPython
-      version 3 releases designated for testing across OpenStack
-      releases.
-    check:
-      jobs:
-        - openstack-tox-pep8
-        - openstack-tox-py35
-        - openstack-tox-py36
-        - openstack-tox-py38
-    gate:
-      jobs:
-        - openstack-tox-pep8
-        - openstack-tox-py35
-        - openstack-tox-py36
-        - openstack-tox-py38
-
-- project-template:
-    name: openstack-python3-charm-yoga-jobs
-    description: |
-      Runs unit tests for an OpenStack Charm project under the CPython
-      version 3 releases designated for testing across OpenStack
-      releases from Yoga onwards.
-    check:
-      jobs:
-        - openstack-tox-pep8
-        - openstack-tox-py36
-        - openstack-tox-py38
-        - openstack-tox-py39
-    gate:
-      jobs:
-        - openstack-tox-pep8
-        - openstack-tox-py36
-        - openstack-tox-py38
-        - openstack-tox-py39
-
 - project-template:
     name: openstack-python3-zed-jobs
     description: |
@@ -818,6 +780,23 @@
       jobs:
         - publish-openstack-python-branch-tarball
 
+- project-template:
+    name: openstack-python3-charm-yoga-jobs
+    description: |
+      Runs unit tests for an OpenStack Charm project under the CPython
+      version 3 releases designated for testing across OpenStack
+      releases from Yoga onwards.
+    check:
+      jobs:
+        - openstack-tox-pep8
+        - openstack-tox-py38
+        - openstack-tox-py310:
+            voting: false
+    gate:
+      jobs:
+        - openstack-tox-pep8
+        - openstack-tox-py38
+
 - project-template:
     name: openstack-python3-xena-jobs
     description: |
@@ -1476,6 +1455,15 @@
     gate: *openstack-python3-latest-gate-jobs
     post: *openstack-python3-latest-post-jobs
 
+- project-template:
+    name: openstack-python3-charm-jobs
+    description: |
+      Runs unit tests for an OpenStack Charm project under the CPython
+      version 3 releases designated for testing the latest release.
+      This will be updated at the start of each new release.
+    check: *openstack-python3-latest-check-jobs
+    gate: *openstack-python3-latest-gate-jobs
+
 - project-template:
     name: openstack-python35-jobs
     description: |