Migrate to using LibrePCB-parts-generator Entities

[z3ugma]

Migrate to the Entities in https://github.com/LibrePCB/librepcb-parts-generator/tree/master/entities

I basically reinvented the wheel for this EasyEDA serializer and will probably switch to importing these instead
As referenced in IDEAS.md

[z3ugma]

Requires some work in the upstream:
LibrePCB/librepcb-parts-generator#65
LibrePCB/librepcb-parts-generator#145
LibrePCB/librepcb-parts-generator#144

[z3ugma]

4e000e3 solves the current install. Once the 3 librepcb-parts-generator fixes are merged into main then the whole issue can close.