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