GeometryStreamBuilder (#965)

### Change list

- Instead of using really complex code to figure out which underlying
array to push each individual `xy` call to, we use an underlying
`GeoWriter` to collect each geometry into a scratch buffer, and then
push that geometry using our existing `push_geometry` APIs. This
simplifies the code a _lot_.
- It may have a negative performance impact because we're allocating
extra heap buffers for the small vecs. In the future, if we want to
optimize this, we may want to create a version of `geo-types` that uses
something like bumpalo

Closes #365

python/pyo3-geoarrow/src/ffi/from_python/scalar.rs

@@ -2,8 +2,7 @@ use std::sync::Arc;
 
 use crate::array::*;
 use crate::scalar::*;
-use geoarrow::datatypes::Dimension;
-use geoarrow::io::geozero::ToMixedArray;
+use geoarrow::io::geozero::ToGeometryArray;
 use geoarrow::scalar::GeometryScalar;
 use geozero::geojson::GeoJsonString;
 use pyo3::exceptions::PyValueError;
@@ -24,9 +23,9 @@ impl<'a> FromPyObject<'a> for PyGeometry {
             // Parse GeoJSON to geometry scalar
             let reader = GeoJsonString(json_string);
 
-            // TODO: we need a dynamic dimensionality reader
+            // TODO: use ToGeometry directly in the future?
             let arr = reader
-                .to_mixed_geometry_array(Dimension::XY)
+                .to_geometry_array()
                 .map_err(|err| PyValueError::new_err(err.to_string()))?;
             Ok(Self(
                 GeometryScalar::try_new(Arc::new(arr))