CI tests config: Define and reuse the pybasever variable

This will make future changes easier to backport to other Python versions.

Note that with jinja2 expressions, we need to quote them to preserve valid yaml, see:
https://docs.ansible.com/ansible/latest/user_guide/playbooks_variables.html#when-to-quote-variables-a-yaml-gotcha

tests/tests.yml

@@ -15,39 +15,40 @@
     repositories:
     - repo: "https://src.fedoraproject.org/tests/python.git"
       dest: "python"
+    pybasever: "3.11"
     tests:
     - rpm_qa:
         run: rpm -qa
     - smoke:
         dir: python/smoke
-        run: VERSION=3.11 ./venv.sh
+        run: "VERSION={{ pybasever }} ./venv.sh"
     - smoke_virtualenv:
         dir: python/smoke
-        run: VERSION=3.11 METHOD=virtualenv ./venv.sh
+        run: "VERSION={{ pybasever }} METHOD=virtualenv ./venv.sh"
     - debugsmoke:
         dir: python/smoke
-        run: PYTHON=python3.11d TOX=false VERSION=3.11 ./venv.sh
+        run: "PYTHON=python{{ pybasever }}d TOX=false VERSION={{ pybasever }} ./venv.sh"
     - selftest:
         dir: python/selftest
-        run: VERSION=3.11 X="" ./parallel.sh
+        run: "VERSION={{ pybasever }} X='' ./parallel.sh"
     - debugtest:
         dir: python/selftest
-        run: VERSION=3.11 PYTHON=python3.11d X="" ./parallel.sh
+        run: "VERSION={{ pybasever }} PYTHON=python{{ pybasever }}d X='' ./parallel.sh"
     - debugflags:
         dir: python/flags
-        run: python3.11d ./assertflags.py -O0
+        run: "python{{ pybasever }}d ./assertflags.py -O0"
     - marshalparser:
         dir: python/marshalparser
-        run: VERSION=3.11 SAMPLE=10 test_marshalparser_compatibility.sh
+        run: "VERSION={{ pybasever }} SAMPLE=10 test_marshalparser_compatibility.sh"
     required_packages:
     - gcc  # for extension building in venv and selftest
     - gcc-c++ # for test_cppext
     - gdb  # for test_gdb
-    - python3.11  # the test subject
-    - python3.11-debug  # for leak testing
-    - python3.11-devel  # for extension building in venv and selftest
-    - python3.11-tkinter  # for selftest
-    - python3.11-test  # for selftest
+    - "python{{ pybasever }}"  # the test subject
+    - "python{{ pybasever }}-debug"  # for leak testing
+    - "python{{ pybasever }}-devel"  # for extension building in venv and selftest
+    - "python{{ pybasever }}-tkinter"  # for selftest
+    - "python{{ pybasever }}-test"  # for selftest
     - tox  # for venv tests
     - virtualenv  # for virtualenv tests
     - glibc-all-langpacks # for locale tests