Clarify SedonaUtils documentation

[rbavery]

It's unclear where to import SedonaUtils from since the import statement is not shown. Searching the documentation for SedonaUtils only reveals this page

https://sedona.apache.org/1.5.1/api/sql/Raster-visualizer/?h=sedonauti#rs_asimage

Ideally that page would show an end to end example of raster visualization that could be run in a notebook.

Additionally, the callout This is not recommended for large files. could specify what is meant by "large files" and the time to visualize an example large file with SedonaUtils.

[rbavery]

this import statement seems redundant

https://github.com/apache/sedona/blob/bedea9a03b29c1bbc0a4739f5308daac685aeddd/python/tests/raster_viz_utils/test_sedonautils.py#L20C1-L20C56

do we need to wrap the display_image function in a class?