Add openstack-tox-py313 jobs

Add jobs for running Python 3.13 via pyenv.  At the time of writing 3.13
is still in the Beta/RC phase.

Discussions on #opendev[1] conclude that for now builing python on demand
it the right balance of speed (access to new python versions), job runtime
and job maintainability in the long term.

[1] https://meetings.opendev.org/irclogs/%23opendev/%23opendev.2024-06-26.log.html#t2024-06-26T22:08:35

Change-Id: I0b10edcbcc22b35a7ac1368f7097a89934620e32

zuul.d/jobs.yaml

@@ -379,6 +379,36 @@
 
       Uses tox with the ``py312`` environment in arm64 platform.
 
+- job:
+    name: openstack-tox-py313
+    parent: openstack-tox
+    nodeset: ubuntu-noble
+    timeout: 2400
+    description: |
+
+      Run unit tests for an OpenStack Python project under cPython
+      version 3.13.
+
+      Uses tox with the ``py313`` environment.
+    irrelevant-files: *common-irrelevant-files
+    vars:
+      tox_envlist: py313
+      bindep_profile: test py313
+      python_use_pyenv: True
+      python_version: '3.13'
+
+- job:
+    name: openstack-tox-py313-arm64
+    parent: openstack-tox-py313
+    nodeset: ubuntu-noble-arm64
+    timeout: 3600
+    description: |
+
+      Run unit tests for an OpenStack Python project under cPython
+      version 3.13 on top of arm64 architecture.
+
+      Uses tox with the ``py313`` environment in arm64 platform.
+
 - job:
     name: openstack-tox-pypy
     parent: openstack-tox