Modernizing the packaging of the library

[Zeitsperre]

Hi,

I'm wondering if it would be alright if I went and rewrote the packaging, testing, and linting configurations using the new TOML format (pyproject.toml) and removed several redundant files from the repository (requirements*.txt, MANIFEST.in, etc.); Linting and other tooling changes would help with potential security and code optimization issues.

If possible, I'd also ask if I can go about replacing setuptools with something a little simpler: flit/flit-core does more than we need here (and is also available on Debian: https://packages.debian.org/source/forky/x32/flit).

[fmigneault]

👍 for the requirements, MANIFEST, etc. switch to pyproject.toml

❓ For flit, I am not sure if it supports some compilation features that could be needed by other packages that use the default setuptools anyway? Quick google search showed that it does not support C/C++/Rust. Is that problematic? Maybe not as critical with #699 if such requirements (GDAL, NetCDF, GeoTiff, etc.?) are pushed downstream.