Added option to update Symbology using JSON files. Style categories are defined using Arcade expressions rather than the SYMBOLOGY field. This lays the groundwork for not having to have the Update Symbology server task.
This updates the feature layer itself, not any web map using it. The layer can be removed and readded to a web map to pick up the changes, or the AGO Assistant can be used to copy JSON templates into the web map for Point, Line, and Polygon Location layers.