ci: create a quality assurance workflow - #173

The package is installed under `lib/python3.X/site-packages/monoprop` all other artifacts are installed in subfolders of it: * `libmonoprop.so` is under `lib` (or `lib64`, depending on the machine)
* all headers are under `include` with the proper hierarchical folder structure
* CMake helper files are under `cmake`  The header files are now explicitly listed (instead of globbed) and we use `target_sources` with `FILE_SET` pento handle them sanely (instead of appending to a global list)

I have dropped the distinction between private and public for now.

Signed-off-by: Roberto Di Remigio Eikås <robertodr@users.noreply.github.com>

There is a single job running on ubuntu-26.04 with python 3.11
collecting coverage information from:
* Python tests
* C++ unit tests
* line hits from calling the C++ compiled code from the Python API

Thus avoiding a rebuild when invoking pytest

Fallout from removing most of the cmake presets

Needs lcov format, plus some workarounds, to merge the Python and C++
results.

… monoprop target