WIP: remove GeometryBasics and GeometryTypes as deps

[sjkelly]

This leaves only the isosurface function which should be trivial to compose with other point types, and mesh types.

TODO:

• [ ] tests
• [ ] docs

This addresses several bitrots and would make this package a little more durable against high level changes and ecosystem changes. This mimics the design of the Contour.jl package in spirit.