CI(build-tools): Update Python from 3.9.2 to 3.9.18 (#6615)

## Problem

We use an outdated version of Python (3.9.2)

## Summary of changes
- Update Python to the latest patch version (3.9.18)
- Unify the usage of python caches where possible

.github/actions/run-python-test-set/action.yml

@@ -86,11 +86,10 @@ runs:
         fetch-depth: 1
 
     - name: Cache poetry deps
-      id: cache_poetry
       uses: actions/cache@v3
       with:
         path: ~/.cache/pypoetry/virtualenvs
-        key: v1-${{ runner.os }}-python-deps-${{ hashFiles('poetry.lock') }}
+        key: v2-${{ runner.os }}-python-deps-${{ hashFiles('poetry.lock') }}
 
     - name: Install Python deps
       shell: bash -euxo pipefail {0}