Consolidate ItemCRS field extraction and common patterns

As noted in https://github.com/apache/sedona-db/pull/535#discussion_r2719780471, the pieces of code where we extract and/or iterate over and/or separate "item"s from "crs"es in kernels that support item crs have been duplicated several times. I struggled to abstract this initially because I wasn't sure which patterns would get repeated. When we have implemented most functions we should circle back to remove duplicated patterns (and bcakport any abstractions or helpers that were invented along the way to previous changes!).

This is particularly useful for implementing raster functions, which will need to iterate over both the geometry and the crs.

Start with the discussion linked from the issue and inspect the kernels that extract, iterate over, or separate items and CRSes. Identify the repeated patterns across those kernels; done means they use shared abstractions or helpers that also support iterating over geometry and CRS for future raster functions.

Written by the indexing model from the issue text.