This is the standard approach and avoids relying on
VCPKG_INSTALLATION_ROOT and -DCMAKE_TOOLCHAIN_FILE= in the ci-windows.py
script.
This makes it easier to run locally.
This is mostly a refactor, except for using the runner workspace (cwd) for:
* fuzz qa-assets
* functional temp prefix
This makes it easier to run the ci-windows.py locally.
This makes it easier to:
* Run the exact command of any CI type and step locally
* Re-Run older CI tasks on GHA and using the latest merged config.
(.github/ci-windows.py is merged with master on re-runs, but
.github/workflows/ci.yml is NOT)
Also, writing it in Python has benefits:
* Any developer (even non-Windows ones) can read and modify the script.
* Python is already required for tests, so no new dependency is needed.