SVG Image module should provide new widget instead of overriding core image

Problem/Motivation

When saving a field that was originally created with image, before svg image was installed, the config changes dependencies and replaces image with svg_image. This module should provide a new formatter instead of overriding the core image formatter.

Another unintended consequence is that all image fields, whether or not they use the svg image settings, now have extra config that is not used.

This issue feels all too familiar since I created the Drupal 7 issue about the same thing https://www.drupal.org/project/svg_image/issues/2974731 →

Proposed resolution

Instead of overriding core, create a new widget.

Remaining tasks

User interface changes

API changes

This would break existing support for sites using the core image formatter with SVG. It would be best to release this as a new major version with an update path. One could scan for SVG files attached to entities and update the widgets on those that are known to use SVG.

Data model changes

Release notes snippet