CI: Use astral-sh/setup-uv action

.github/workflows/test.yml

@@ -32,11 +32,18 @@ jobs:
           python-version: ${{ matrix.python-version }}
           cache: 'pip'
           cache-dependency-path: 'py.requirements/*.txt'
+      - name: setup-uv -- Speed-up Python package installations ...
+        uses: astral-sh/setup-uv@v3
+        with:
+          enable-cache: true
+          cache-dependency-glob: |
+            **/pyproject.toml
+            **/py.requirements/ci.github.testing.txt
+            **/py.requirements/basic.txt
       - name: "Install Python package dependencies (with: uv)"
         run: |
-          python -m pip install -U uv
           python -m uv pip install -U pip setuptools wheel
-          python -m uv pip install --upgrade -r py.requirements/ci.github.testing.txt
+          python -m uv pip install -U -r py.requirements/ci.github.testing.txt
           python -m uv pip install -e .
       - name: Run tests
         run: pytest