ADBC: add spatial support for DuckDB databases and GeoParquet

[rouault]

• Automate loading duckdb_spatial extension when installed, and when the dataset is DuckDB or Parquet
• Retrieve geometries (GEOMETRY type) as OGR geometries
• Read GeoParquet metadata to figure out spatial extent, CRS and geometry type per geometry column
• Use duckdb_spatial ST_Intersects() for faster spatial filtering (when done with OGRLayer::SetSpatialFilter()), potentially leveraging DuckDB RTree when it is available.
• Use GeoParquet bounding box column in complement to above
• Passthrough forward of WHERE claused expresse through OGRLayer::SetAttributeFilter()

[coveralls]

coverage: 68.541% (-0.04%) from 68.579%
when pulling e7332ae on rouault:adbc_spatial
into d511807 on OSGeo:master.

[paleolimbot]

This is amazing! I looked through for anything that seemed off about ADBC usage but it seems great. We've talked about providing a libpq-like "escape string"/"escape identifier" to help with people generating SQL, but here you're mostly generating SQL destined for a specific source.

The Snowflake, BigQuery, and PostgreSQL drivers also can have geometry queried...eventually I think we'll have them marked with the "geoarrow.wkb" extensions (hopefully also from DuckDB eventually).