Fix: address feedback for Fedora package

[emansom]

This PR addresses feedback by @NeilHanlon from the Fedora package review request upstream here.

It was tedious to get the packaging thing to work alright, I opted for a semi hack in __init__.py as for some reason I couldn't get the setuptools packaged with EL to expand smfc.py to a full namespace. Inform me if there's a better way: i'm very much a novice in Python.

Multiple Python build system compatibility layers are implemented: that's why there's an setup.cfg, setup.py and pyproject.toml that all contain the same definitions. This is to get the same behavior across all distros: EL ships with old setuptools and old pyproject that don't behave the same as their latest versions would.

Split the files for better maintainability and sanity. Currently this does break the Docker support, will fix this before merge (hence it's a draft).

Per feedback I have replaced all /opt references with /etc. The .spec file has further been enhanced to build and test the smfc code. Package has also been split in two: smfc and python3-smfc as dependency.

The file structure has been altered to a flat package structure to make pyproject happy. Further several system-wide files have been moved to more descriptive directories.

[petersulyok]

Fundamental changes. I will move the PR to a branch while it is stabilizing and I understand what is happening.