Switch to meson build system and provide SLICOT natively

[ilayn]

I am quite guilty of ignoring this lib since life happened and I decided to do more on SciPy side. However, on the SciPy side, we (not me but quite able folks of SciPy) managed to switch to a new build system Meson and surprisingly (my stupidity considered) I kinda get how it works.

This means I can actually (and finally) compile SLICOT on all major platforms and incorporate into harold then place it on PyPI without rewriting everything. First I tried to push this into scipy.signal module but got resistance and eventually became a cold case. Thus harold might be a better fit. But most probably there will be a a major backwards compatibility breakage. Not necessarily API-wise but maybe also result-wise. I am not sure if many people use this library hence I can probably ping all the users myself ;-)

There are a few more things to incorporate but if anyone is still reading this, please share your ideas here about harold version X.X