Allow vectors with mixed single and multi geometries to be plotted in Makie

[asinghvi17]

This upstreams GeoMakie.to_multipoly and its variants into GeoInterfaceMakie. Performance needs improvement but this is otherwise ready for review, and I have tested it works.

Usecase:

using NaturalEarth
using CairoMakie

fc = NaturalEarth.naturalearth("admin_0_countries", 10)
plot(fc.geometry)

without any fuss or muss.

[asinghvi17]

Currently this only allows vectors of (poly, multipoly) or (linestring, multilinestring). Should we also allow GeometryCollections, and just assume that GeoMakie or GeometryOps will do some piracy to allow plotting those, maybe an error hinter or something?

GeoMakie's to_multipoly implementation has such a method but it could also be a GeometryOps extension on GeoInterfaceMakie.

[rafaqz]

Not sure GeometryOps should get involved here, that's some messy piracy... Why not deal with GeometryCollection here too?

[asinghvi17]

Hmm I guess we can assume gc's are well formed...

[00krishna]

Do you need any additional input from me @asinghvi17 ? I am good with whatever you choose.

[asinghvi17]

I think this approach is good, only problem is that GeometryBasics doesn't support geometry collections. I guess I'd have to rewrite the logic to check for traits then dispatch accordingly instead of eagerly converting.

[rafaqz]

Can we just convert to vector and hit the other vector methods in this PR?

[asinghvi17]

What do you mean? Just skipping GeometryCollection support?

[rafaqz]

No, just collect GI.getgeom on the geometry collection and call the method again to get Vector dispatch and the Union branch you defined in this PR

[asinghvi17]

For the plot type that ought to work - the problem is that there's no GB convert defined, so the convert_arguments for vectors will fail. Just have to reorder the evaluations and check traits first...