* A basic Poetry project for managing dev scripts and tools
  Fixup several other scripts to be set -u safe since we now import that
  setting.
* Use Poetry to run Sphinx
* Change variant used for release archive
  The release archive build invokes Sphinx, and since Sphinx is now installed by
  Poetry, we require a newer Python version. make-release-archive now runs
  on Ubuntu 22.04
* abi-compliance-check needs u18
  The abi-compliance-check task assumes an external `abi-compliance-checker`
  tool is installed, but that is only true on the Ubuntu 18.04 EVG
  distros.
* Significant script refactoring:
- Split components into separate files, and provide a way to selectively
  import them from other scripts.
- Download install-poetry.py on-the-fly when it is needed, not committed
  into the repository.
- Add a download-file utility.
- python.sh/poetry.sh are importable to be reused in other scripts.
* Add notes about building docs to CONTRIBUTING
* Parallelize the HTML build
* Add a console script for EVG generation

Added full support for win32 (mingw / msvc)

This means we don't need to do a double mmap() and also means we can
handle an incomplete set up shared memory area.

This should be more readable and easier to debug. Additionally, we try
to cleanup our shared memory segment on shutdown with atexit(). If the
process exits uncleanly, we have the benefit of being able to extract
the counter information after the fact.