windows-2019 will be fully retired by the end of June, and 2025 is the latest version.
This means that Windows build artifacts will be built using MSVC 2022, not MSVC 2019. They should be ABI-compatible across this change, since they expose no third-party types and Microsoft say that their compiler and standard library didn't break ABI between 2019 and 2022, but a newer version of the redistributable might be needed.
windows-2016 was scheduled for removal in April 2022, though the
previous commit's build still worked.
This also means that the MSVC 2019 redistributable is now required.
Although libloot 0.15 is built with MSVC 2017, 2019 can link code
build with 2017 and the 2019 redistributable effectively replaces
the 2017 redistributable, so there's no compatibility issues.
So that the wrapper library can be installed with `pip install
<archive>`. The setup.py is Windows-specific, but CI only
produces Windows builds so that's not currently an issue.
The __init__.py re-exports the .pyd module so that the .pyd and
.dll can be installed into a subdirectory of site-packages for
neatness, and so that the installed module isn't just to work
around pip install being unable to install a pyd with no package.