Bugfix 2.4.12 (phoebe-project#797)

* upgrade the build system to pyproject.toml with setuptools as backend and pip as frontend.
* drop the dependency on the obsolete distutils module.
* swap nosetests for pytest.
* small build-related bugfixes throughout the code.

---------

.github/workflows/on_pr.yml

@@ -0,0 +1,94 @@
+name: Latest per-python environments
+
+on:
+  workflow_dispatch:
+  pull_request:
+  push:
+    branches:
+      - 'master'
+      - 'feature-*'
+      - 'bugfix-*'
+
+jobs:
+  build:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: ["3.7", "3.8", "3.9", "3.10", "3.11"]
+        os: [ubuntu-latest, macos-latest]  # https://docs.github.com/en/actions/using-github-hosted-runners/about-github-hosted-runners
+        toolchain:
+            - {compiler: gcc, version: 13}  # https://github.com/fortran-lang/setup-fortran
+
+    name: ${{ matrix.os }} python${{ matrix.python-version}}
+    steps:
+    - name: Checkout PHOEBE
+      uses: actions/checkout@v4
+
+    - name: Setup python ${{ matrix.python-version }}
+      uses: actions/setup-python@v4
+      with:
+        python-version: ${{ matrix.python-version }}
+
+    - name: PHOEBE environment variables
+      run: |
+        export PHOEBE_ENABLE_PLOTTING='FALSE'
+        export PHOEBE_UPDATE_PASSBAND_IGNORE_VERSION='TRUE'
+
+    - name: Update pip
+      run: |
+        python -m pip install --upgrade pip
+
+    - name: Install phoebe optional modules
+      run: |
+        python -m pip install rebound
+
+    - name: Install PHOEBE from source
+      run: |
+        pip install .
+
+    - name: Install and run pipdeptree to see package dependencies
+      run: |
+        python -m pip install pipdeptree
+        pipdeptree
+
+    - name: Checkout photodynam
+      uses: actions/checkout@v4
+      with:
+        repository: phoebe-project/photodynam
+        path: photodynam
+
+    - name: Install photodynam
+      run: |
+        cd photodynam
+        make
+        sudo cp photodynam /usr/local/bin/
+        python setup.py build && python3 setup.py install --user
+        cd ..
+
+    - name: Test photodynam install
+      run: |
+        python -c "import photodynam"
+
+    - name: Setup GNU Fortran
+      id: setup-fortran
+      uses: fortran-lang/setup-fortran@v1
+
+    - name: Install jktebop
+      env:
+        FC: ${{ steps.setup-fortran.outputs.fc }}
+      run: |
+        wget https://www.astro.keele.ac.uk/jkt/codes/jktebop-v43.tgz
+        tar -xvzf jktebop-v43.tgz
+        cd jktebop43
+        ${{ env.FC }} -o jktebop jktebop.f
+        echo $(pwd) >> $GITHUB_PATH
+        cd ..
+
+    - name: Test jktebop install
+      run: |
+        jktebop
+
+    - name: Run tests
+      run: |
+        pytest --verbose --capture=no tests/tests/