Prep work for to_wkt

[kylebarron]

Change list

• Convert geo-traits scalars to wkt::Wkt
• This is prep work for direct transformation of geoarrow scalars to wkt::Wkt objects.
• This does not go through geozero, partially because I hit issues with multidimensional writing in https://github.com/georust/geozero/pull/237
• This supersedes https://github.com/geoarrow/geoarrow-rs/pull/788, though it hasn't yet piped through to a full ToWkt trait implemented on arrays. cc @b4l

In the future, hopefully geo-traits will be standardized and we'll be able to pass trait objects directly to wkt's APIs

For https://github.com/geoarrow/geoarrow-rs/issues/762