🐛 Fix test_dsl for pytest>=8.3.0 (#845)

- The new version of `pytest` (>=8.3.0) does not update variables properly in different scenarios. This causes the tests to fail. As a fix I have nested variables in a dictionary and then parse them for each function.
- Remove pin from `pytest` version.

.github/workflows/python-package.yml

@@ -30,7 +30,7 @@ jobs:
         sudo apt update
         sudo apt-get install -y libopenslide-dev openslide-tools libopenjp2-7 libopenjp2-tools
         python -m pip install --upgrade pip
-        python -m pip install ruff==0.5.7 "pytest<8.3.0" pytest-cov pytest-runner
+        python -m pip install ruff==0.5.7 pytest pytest-cov pytest-runner
         pip install -r requirements/requirements.txt
     - name: Cache tiatoolbox static assets
       uses: actions/cache@v3

requirements/requirements_dev.txt

@@ -7,7 +7,7 @@ mypy>=1.6.1
 pip>=22.3
 poetry-bumpversion>=0.3.1
 pre-commit>=2.20.0
-pytest>=7.2.0, <8.3.0
+pytest>=7.2.0
 pytest-cov>=4.0.0
 pytest-runner>=6.0
 pytest-xdist[psutil]