"Prepared geometry" is basically a regular geometry with an attached cache, which can be a sorted edge list, an Rtree, a monotone chain decomposition, etc.

We should create prepared geometry wrapper structs which hold a geometry + its cache. It may also contain a field verifying whether the geometry has been validated or not. (This will require special handling in e.g. apply, probably).

Preparations would also require an interface, both to create them, and a trait like interface where we can use multiple libraries' implementations (LibSpatialIndex.jl, SortTileRecursiveTree.jl, NearestNeighbors.jl, etc.)

The wrapper would also have to wrap feature collections, so we can use rtrees defined in things like .gpkg files or elsewhere for spatial joins etc.