feat(sedona-gdal): add convenience facade and mem builder

[Kontinuation]

Summary

• add the high-level Gdal facade and with_global_gdal convenience entry point
• add the MEM dataset builder on top of the lower-level dataset and raster wrappers
• keep the top-level API explicit by importing concrete raster/vector modules instead of relying on wrapper re-export aliases

Depends on #698.

Testing

• cargo test -p sedona-gdal
• cargo clippy -p sedona-gdal -- -D warnings

[Copilot]

Pull request overview

This PR introduces a higher-level ergonomics layer for sedona-gdal by adding a Gdal facade and a fluent MEM dataset builder, while keeping the lower-level API available for explicit use.

Changes:

• Add Gdal high-level facade wrapping &'static GdalApi to reduce explicit api plumbing at call sites.
• Add MemDatasetBuilder for constructing MEM datasets (including zero-copy band attachment plus optional geotransform/projection/nodata).
• Export call_gdal_api! as a macro and add with_global_gdal convenience entry point.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
c/sedona-gdal/src/mem.rs	New MEM dataset builder and MEM dataset creation helper + tests.
c/sedona-gdal/src/lib.rs	Exposes the new gdal and mem modules publicly.
c/sedona-gdal/src/global.rs	Adds with_global_gdal convenience wrapper around the global API handle.
c/sedona-gdal/src/gdal.rs	New Gdal facade providing ergonomic wrappers for common operations.
c/sedona-gdal/src/gdal_api.rs	Exports call_gdal_api! macro (now public/root-exported).

Comments suppressed due to low confidence (1)

c/sedona-gdal/src/gdal_api.rs:48

• call_gdal_api is now marked #[macro_export], which makes it part of the public API and exports it at the crate root. However, the macro expands to $api.inner.$func, and inner is pub(crate), so downstream crates cannot actually use the exported macro (privacy check will fail). Consider removing #[macro_export] and keeping it crate-internal (the existing pub(crate) use call_gdal_api; already enables use across this crate without widening the public surface).

#[macro_export]
macro_rules! call_gdal_api {
    ($api:expr, $func:ident $(, $arg:expr)*) => {
        if let Some(func) = $api.inner.$func {
            func($($arg),*)
        } else {
            panic!("{} function not available", stringify!($func))
        }
    };
}

pub(crate) use call_gdal_api;

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[paleolimbot]

A few optional things that may be worth considering. Thank you!

[paleolimbot]

This is so cool

[paleolimbot]

These are all a bit light on the documentation (maybe they could link to the underlying implementation's docs which I seem to remember have a bit more depth?). Also OK to defer since this is mostly intended to be for internal usage.

[paleolimbot]

I do like the idea of a high-level object that dishes out other safe high-level objects, although putting it all here involves repeating some documentation (or omitting it) and I'm not sure it's needed given that the constructors it refers to are pub anyway. Reexporting the structs or functions that are part of the intended external API might be another way to expose the API without loosing the docs?

[paleolimbot]

Is this actually WKT or can this by anything? (It may be less error prone to accept anything or an explicit spatialref object)

[paleolimbot]

Is this actually required to be mutable? (This seems like a strange constraint, and also one that will result in it not being particularly useful to us)

[paleolimbot]

Are you sure the data pointer has to be mutable? (This would preclude backing a GDAL mem dataset with Arrow data?)