[GMSH] Finish porting meshing

[simbilod]

Tests are now passing and meshes generated, but some things still need to be ported better

• [ ] don't hardcode the database unit when converting KLayout polygons to shapely for passing into meshwell
• [ ] consider doing the polygon preprocessing in KLayout instead of shapely (only convert to shapely when interfacing with meshwell)
• [ ] fix edge ports
• [x] fix get_component_with_net_layers
• [ ] figure out issues with meshbool and physical overrides not being default=None
• [ ] fix warnings

[simbilod]

get_component_with_net_layers fixed in #469 , thanks @mdecea