Also fixes various bugs if symbols contained non-indexed pin numbers.
We really need to know the actual pin names when creating models, rather
than just assuming 1, 2... etc.
Fixes https://gitlab.com/kicad/code/kicad/issues/13183
Follow-up after the KIBIS and KIBIS GUI merge requests.
- Move KIBIS from Pcbnew to Eeschema space,
- Make KIBIS obtain the Ku/Kd coefficients via the `SPICE_SIMULATOR` class instead of calling the `ngspice` executable via `system()`,
- Allow to toggle between differential and single-ended model in the GUI,
- Various GUI fixes and improvements.