Move tests into main workflows.

The workflow UI works best if there's only a single main workflow in a
PR. We can keep things organized similarly by turning the test workflow
into a reusable workflow. Same code (mostly), better UI.

.github/workflows/test.yml

@@ -1,30 +1,16 @@
-name: Test
-
-on: [push, pull_request]
-
+name: Tests
+on: workflow_call
 jobs:
-  build:
+  python-tests:
+    name: Python tests
     runs-on: windows-latest
     steps:
       - uses: actions/checkout@v2
         with:
           submodules: true
 
-      - name: Set up Python
-        uses: actions/setup-python@v2
-        with:
-          python-version: "3.10"
-
-      - name: Install environment
-        run: |
-          python -m venv ./venv
-
-      - name: Install dependencies
-        run: |
-          ./venv/scripts/activate
-          python -m pip install -r requirements.txt
-          # For some reason the shiboken2.abi3.dll is not found properly, so I copy it instead
-          Copy-Item .\venv\Lib\site-packages\shiboken2\shiboken2.abi3.dll .\venv\Lib\site-packages\PySide2\ -Force
+      - name: Set up Python environment
+        uses: ./.github/actions/setup-liberation-python
 
       - name: run tests
         run: |