CI/Doc: Use pytest subtests (#986)

* CI/Doc: use pytest-subtests

* CI: clean up pip installs a bit

* make lint and unittests install the same stuff
* make sure to install wheel, which is a recommended (not required) dependency for everything pip

.github/workflows/lint.yml

@@ -18,8 +18,8 @@ jobs:
         python-version: 3.9
     - name: Install dependencies
       run: |
-        python -m pip install --upgrade pip
-        pip install flake8 pytest
+        python -m pip install --upgrade pip wheel
+        pip install flake8 pytest pytest-subtests
         if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
     - name: Lint with flake8
       run: |