Define testing runtime for 2024.2 release

Below are the changes from previous cycle
testing runtime:

* Removing python 3.8 support because it is EOLing in oct 2024[1]
  which means python 3.9 will be the minimum python version in
  testing runtime.

* Add Python 3.12 as non voting testing.

* Remove Debian 11 from Additional testing support because 2024.2
  is non-SLURP release and previous SLURP release 2024.1 supported
  Debian 12 also which is what can be used as smooth upgrade to
  future SLURP release 2025.1

* Removing Nodejs from runtime:
  Nodejs is not a runtime requirement for Horizon instead it is
  one of the test dependency. It does not fit as a runtime and can
  be handle by Horizon team based.

* For better clarity, changed the 'Best Effort' section to
 'Advance/Unstable Testing'. Adding Ubuntu 24.04 in that list.

[1] https://devguide.python.org/versions/

Change-Id: I77dbbf2413074ce0cddbfe6ac2f29d0ee1d71921

reference/runtimes/2024.2.rst

@@ -0,0 +1,92 @@
+.. _2024-2-testing-runtime:
+
+==========================
+Tested Runtimes for 2024.2
+==========================
+
+Linux Distribution
+==================
+
+At the start of the 2024.2 development cycle, the current :ref:`LTS or stable
+distribution <pti-linux-distros>` versions are:
+
+* Ubuntu 22.04
+* Debian 12
+
+Additional testing for a smooth upgrade
+---------------------------------------
+
+* None
+
+Python
+======
+
+It is the :doc:`policy <../../resolutions/20181024-python-update-process>` that
+each OpenStack release cycle will target the latest available version of
+Python; default Python runtime on the distributions listed above; and versions
+used in integration tests at the start of the cycle, at least until the point
+when all projects have migrated to a later version.
+
+Also, as per the Python testing requirements defined in :ref:`pti-python`,
+projects should avoid removing Python versions that have not reached EOL
+without a solid reason.
+
+Based on the criteria above, all Python-based projects must target and test
+against, at a minimum:
+
+* Python 3.9 (available as default in Debian 11 and Centos 9 Stream)
+  Python 3.9 is the the minimum supported/required version for 2024.2.
+  This does not imply that Debian 11 is the minimum supported distribution
+  but it may be used for tox testing. supporting Python 3.9 does not require
+  full tempest testing, but py39 unit tests are expected as a minimum
+  requirement for all Python projects. The minimal requirement for
+  testing jobs against Python versions above is to ensure language compatibility,
+  having more extensive testing is allowed.
+
+* Python 3.10 (available as default in Ubuntu 22.04)
+
+  In previous cycle testing, we have not seen many incompatible changes between
+  Python 3.9 and Python 3.10. It is okay to skip running the Python 3.10 testing
+  jobs assuming that anything that works on Python 3.9 and 3.11 will also
+  work on 3.10.
+
+  Note: as most tempest jobs run on Ubuntu 22.04, it is expected that python
+  3.10 will be tested in tempest jobs. As such, it will be transitively tested
+  for compatibility even without explicit unit and functional tests.
+
+* Python 3.11 (available as default in Debian 12)
+
+  This is the upper bound of required testing for 2024.2.
+
+* Python 3.12 (going to be available as default in Ubuntu 24.02)
+
+  This is not mandatory testing in the 2024.2 cycle, and there is no guarantee
+  that the OpenStack 2024.2 release will support Python 3.12.
+
+  .. warning::
+
+     There is a high chance that we might see a lot of failure in Python 3.12
+     and need a good amount of time to fix them. Adding it as non-voting is an
+     effort to start testing and fixing the issues in advance. It is
+     recommended to start the minimal testing in the 2024.2 cycle.
+
+     Python 3.12 will be mandatory testing in a future release.
+
+More details on Python requirements can be found in :ref:`pti-python`.
+
+Advance/Unstable Testing
+========================
+
+The below list is for the distribution/python advance or unstable versions
+to test them in OpenStack CI/CD. These may not be part of integrated testing
+and may be tested as non-blockers or periodically only. The main idea is to
+test them in advance to be part of integrated testing in future
+cycles.
+
+Based on their testing infra setup, instability, or their future
+releases, we can modify the list during any phase of the current development
+cycle.
+
+* CentOS Stream 9
+* Rocky Linux 9
+* Ubuntu 24.04 (supposed to be released at the end of April 2024)