chore: switch to meson as build backend

[rdenham]

What is this PR changing?

Transition to meson as the build backend

Our team is switching to meson as the build backend for all python projects that include compiled code, such as fortran, cython, c++ etc (not rust though, that would use maturin).

This helps us keep up to date with changes in python and numpy. Since some of our projects use geowombat as a dependency, then I was wondering if this sort of approach would be useful to this project as well. It would make building and installing geowombat on python > 3.12 and with numpy >= 2 easier for us.

I've included an example of the transition in the PR, but note that there are a couple of things that probably need work:

• handling version. For now I've just added the version string to pyproject.toml, but I probably should look into a method that aligns with your current approach to setting version
• most tests pass, but I did have a failure with one of the coreg tests which needs looking into
• I unpinned pretty much everything, but this might need to be reviewed.

I've included a Dockerfile to provide an example of how geowombat can be installed for Ubuntu users, the main part is as follows:

RUN cd \
    && uv venv \
    && . .venv/bin/activate \
    && uv pip install gdal[numpy]==$(gdal-config --version)  \
    && uv pip install git+https://github.com/rdenham/geowombat@meson 

(uv is great, but the same should work for standard pip as the packaging frontend system).

Let me know if there is any interest in this and if so I'll do a bit more to make it fully functional.

[eli-schwartz]

The py_mod and py3 variables established in the root meson.build file are available for use here as well.

While you are at it, you may choose to do dependency lookups (dependency()) a single time in the root meson.build file as well, rather than once per subdir using it. The lookups are cached either way so it won't re-run the finders (numpy-config etc.), but it will emit additional log lines.

[eli-schwartz]

Since meson 0.64, you can use pure: false in "find_installation" and it will be the defaulted value for each "install_sources" call, which lets you save a bit on DRY.