[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
• 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

[joamatab]

any updates on this Simon?

[simbilod]

The code gives good outputs, fixing these is not high priority right now. Feel free to close. Happy to give pointers to whoever would want to pick this up.