Python: Scalar FFI import & export (#525)

Starts work on accepting scalar input into functions. Implements
conversions from `__geo_interface__` to geoarrow scalars.

Todo:

- [x] Export geoarrow scalars via `__arrow_c_array__`
- [x] Import geoarrow scalars via `__arrow_c_array__`
- [x] Import geoarrow scalars via `__geo_interface__` (on each scalar
class, not just on the `ScalarInput` wrapper)

Closes #524, closes
#436

python/core/python/geoarrow/rust/core/_rust.pyi

@@ -35,57 +35,87 @@ from .types import (
 from .enums import AreaMethod, LengthMethod, SimplifyMethod
 
 class Point:
+    def __arrow_c_array__(
+        self, requested_schema: object | None = None
+    ) -> Tuple[object, object]: ...
     def __eq__(self, other: Self) -> bool: ...
     @property
     def __geo_interface__(self) -> dict: ...
     def _repr_svg_(self) -> str: ...
 
 class LineString:
+    def __arrow_c_array__(
+        self, requested_schema: object | None = None
+    ) -> Tuple[object, object]: ...
     def __eq__(self, other: Self) -> bool: ...
     @property
     def __geo_interface__(self) -> dict: ...
     def _repr_svg_(self) -> str: ...
 
 class Polygon:
+    def __arrow_c_array__(
+        self, requested_schema: object | None = None
+    ) -> Tuple[object, object]: ...
     def __eq__(self, other: Self) -> bool: ...
     @property
     def __geo_interface__(self) -> dict: ...
     def _repr_svg_(self) -> str: ...
 
 class MultiPoint:
+    def __arrow_c_array__(
+        self, requested_schema: object | None = None
+    ) -> Tuple[object, object]: ...
     def __eq__(self, other: Self) -> bool: ...
     @property
     def __geo_interface__(self) -> dict: ...
     def _repr_svg_(self) -> str: ...
 
 class MultiLineString:
+    def __arrow_c_array__(
+        self, requested_schema: object | None = None
+    ) -> Tuple[object, object]: ...
     def __eq__(self, other: Self) -> bool: ...
     @property
     def __geo_interface__(self) -> dict: ...
     def _repr_svg_(self) -> str: ...
 
 class MultiPolygon:
+    def __arrow_c_array__(
+        self, requested_schema: object | None = None
+    ) -> Tuple[object, object]: ...
     def __eq__(self, other: Self) -> bool: ...
     @property
     def __geo_interface__(self) -> dict: ...
     def _repr_svg_(self) -> str: ...
 
 class Geometry:
+    # def __arrow_c_array__(
+    #     self, requested_schema: object | None = None
+    # ) -> Tuple[object, object]: ...
     def __eq__(self, other: Self) -> bool: ...
     @property
     def __geo_interface__(self) -> dict: ...
     def _repr_svg_(self) -> str: ...
 
 class GeometryCollection:
+    def __arrow_c_array__(
+        self, requested_schema: object | None = None
+    ) -> Tuple[object, object]: ...
     def __eq__(self, other: Self) -> bool: ...
     @property
     def __geo_interface__(self) -> dict: ...
     def _repr_svg_(self) -> str: ...
 
 class WKB:
+    def __arrow_c_array__(
+        self, requested_schema: object | None = None
+    ) -> Tuple[object, object]: ...
     def __eq__(self, other: Self) -> bool: ...
 
 class Rect:
+    def __arrow_c_array__(
+        self, requested_schema: object | None = None
+    ) -> Tuple[object, object]: ...
     def __eq__(self, other: Self) -> bool: ...
 
 class PointArray: