Add RS_Example and support for raster scalars

[jesspav]

Adding RS_Example to allow for quick function testing.

Follow-up - we will make something more interesting in the bands (perhaps add a generated tree canopy or use the values from a real (but tiny) raster. This will be helpful for making more user friendly examples.

Example run:

> Select RS_Width(rs_example());
┌────────────────────────┐
│ rs_width(rs_example()) │
│         uint64         │
╞════════════════════════╡
│                     64 │
└────────────────────────┘

[Copilot]

Pull Request Overview

This PR adds the RS_Example function to provide a quick testing utility for raster operations, and includes support for scalar raster inputs in the executor.

Key Changes:

• Added RS_Example UDF that generates a sample 64x32 raster with 3 bands for testing purposes
• Extended RasterExecutor to handle both array and scalar raster inputs
• Registered the new raster function set in the Sedona context

Reviewed Changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
rust/sedona/src/context.rs	Registers the raster function set to make RS_Example available
rust/sedona/Cargo.toml	Adds sedona-raster-functions dependency
rust/sedona-raster-functions/src/rs_example.rs	Implements RS_Example UDF with sample raster generation logic
rust/sedona-raster-functions/src/register.rs	Registers rs_example_udf in the default function set
rust/sedona-raster-functions/src/lib.rs	Exports the rs_example module
rust/sedona-raster-functions/src/executor.rs	Adds scalar raster support to RasterExecutor with handling for Struct and Null scalars

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[paleolimbot]

Thank you!