* Python Wheel workflow uses `ubuntu-20.04` to fix the build
  * In #2058 I forgot to update `ciwheel.yml`
* Why this is necessarily: still have not figured it out. `cibuildwheel`
builds and tests in it's own container...
  * [x] https://github.com/brenthuisman/arbor/actions/runs/3704419712
* Small change to make `musllinux` wheels build. They don't pass testing
yet, so I don't add them to the workflow but that can be solved/added
[later](https://github.com/pypa/cibuildwheel/issues/1376)
* The reason for using `ubuntu-20.04` in the Spack workflow should [no
longer exist](https://github.com/actions/runner-images/issues/6724).

- It's actually a Github cache trick: https://github.com/actions/cache/issues/342#issuecomment-673371329
  - First run: 1h 7m 38s 
  - Second run: same duration. Hmm....
  - Third run: ~10 minutes!
  - 4th: ~7.5 min.
- Bump in configs: macos 10.15 will disappear in a month: https://github.com/actions/virtual-environments/issues/5583
  - Bump clang-max to 14, gcc-max to 11
  - macos-min to 11, macos-max to 12.

- Generate timestamped VERSION once, to properly group on Test.PyPI. Example:
  - https://github.com/arbor-sim/arbor/actions/runs/2696804929
  - https://test.pypi.org/project/arbor/0.7rc20220719101015/
- Update/simplify release documentation.
- Update to v0.7

* - Weekly CI Python wheel build pushes to Test.PyPI.org
    - Easy availability at https://test.pypi.org/project/arbor/
- Small change in documentation around VERSION
- Delete superfluous setup.py file.

Move Python build to `pyproject.toml`, bump Python minver to 3.7, fix macos wheel generation (#1916)

* Failing Macos Python wheel builds fixed.
* Macos Python wheels now come with dual-arch (x86-64 and arm64)
* Moved (nearly) all Python build instructions to `pyproject.toml`
  * Enables 'build isolation', and need to specify build-deps only once, no need for users or CI scripts to pre-install them.
  * Enables editable `pip` installs (`pip install -e ./arbor`)
  * Compatible with 'build frontends' `pip` and `build`.
  * Passing CMake options actually got shorter
* Drop Python 3.6 support.

Upstream bug: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1006615



Currently affects Ubuntu 22.04 users.

Co-authored-by: Simon Frasch <simon.frasch@cscs.ch>

* bump version to v0.6-rc
* Update `MANIFEST.in` and `scripts/run_python_examples.sh`
* Update Release instructions `docs/contrib/release.rst`
* Fix missing quotes in `python/example/single_cell_nml.py`
* Add testing to sdist creation in `ciwheel.yml`
* Rename `basic.yml` to `test-everything.yml`
   * Remove Python examples step from matrix (mostly because plotting takes much CPU on macos)
   * change to build /w nml
   * add test of pip builds (`pip install` in addition to CMake builds)
      * Python examples are tested here, once is enough.

- build-catalogue
  - now installed by pip
  - enable GPU-backends
  - isolate from being installed in a non-default dir
  - rename to arbor-build-catalogue
  - allow hand-written C++ mechanisms to be linked in the same catalogue.
- CMake
  - enable PIC on arbor always to allow linking to shared objects
  - use relative paths when configuring a-b-c, to make relocation less of a problem
- Python
    - ensure a-b-c is installed by pip, along with headers and libarbor.a
    - throw errors if tools (cmake scripts, arbor package, modcc) missing
    - transition setup.py setuptools -> skbuild.
- Wheels
    - Add NML2 support to wheels
    - scripts/build-wheels.sh builds wheels, in principle valid for submission to PyPI, on your own hardware. This should be kept in sync with .github/workflows/ciwheel.yml
    - scripts/patchwheel.py corrects the rpath in the libraries in the wheels, working around a bad interplay between auditwheel and skbuild, see pypa/auditwheel#363
    - Python Wheels are tested as part of the Github Action 
    - Add nml and bundled status to config().

Don't pass any architecture by default in setup.py to allow for building binary wheels for targets like x86_64.

Build Python package with 'none' arch by default.
Bump version to 0.5.2.

Bump version for release

* Auto-generate binary Python wheels, triggered by git tags 'v*'.
  * Wheels are generated for Python versions 3.6-3.9, for Linux using the [PyPA manylinux-2014 image](https://github.com/pypa/manylinux) and MacOS using macos-latest (10.15 at time of writing).
  * The Action generates `sdist` for any other platforms.
  * The cibuildwheel action automatically prepares the wheels using [auditwheel](https://cibuildwheel.readthedocs.io/en/stable/options/#repair-wheel-command), which means bundling of external deps (e.g. libxml2 for NeuroML).
  * The output is all that's needed for publication of a new version to (Test)PyPI.
* `setup.py` defaults `neuroml` to on.
* A small change to `CMakeLists.txt` was required to build the wheels: based on this [Pybind hint](https://pybind11.readthedocs.io/en/stable/compiling.html#findpython-mode) `Development.Module`is now required, and not `Development` when CMake searches for Python. I confirm this change is needed to make Arbor build in the manylinux docker images, but I do not understand what the change implies, other than that we now don't link to `libpython`.