CI config: update to Fedora 35 and add Python 3.10

Signed-off-by: Adam Williamson <awilliam@redhat.com>

.zuul.yaml

@@ -1,12 +1,12 @@
 - job:
     name: os-autoinst-tox
     run: ci/tox.yaml
-    nodeset: fedora-31-vm
+    nodeset: fedora-35-vm
 
 - job:
     name: os-autoinst-perl
     run: ci/perl.yaml
-    nodeset: fedora-31-vm
+    nodeset: fedora-35-vm
 
 - project:
     check:

ci/tox.yaml

@@ -5,7 +5,7 @@
         name: ensure-tox
     - name: Install all Python versions to test
       package:
-        name: ['python37', 'python38', 'python39']
+        name: ['python37', 'python38', 'python39', 'python310']
         state: present
       become: yes
     - name: Run tox

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 skipsdist = True
-envlist = py37,py38,py39
+envlist = py37,py38,py39,py310
 skip_missing_interpreters = true
 [testenv]
 deps =