Develop an upgrade path from CKEditor4 to CKEditor5 plugin

Problem/Motivation

Follow up from 📌 CKEditor5 Drupalbreaks update Needs review . There were a few folks that reported troubles when updating from 2.x (CKEditor 4) to 3.0.x-dev (CKEditor 5) wherein they needed to re-add the Drupal Breaks button and text filter to their editor config. Would be nice to have an upgrade path so that this is not required.

Steps to reproduce

• Begin on a site that has version 2.x installed with CKEditor 4 configured
• Update to 3.x

Expected results

Configuration for DrupalBreaks on relevant text formats is all set to work correctly on CKEditor 5 without user intervention.

Proposed resolution

Develop the apropriate upgrade path.

Remaining tasks

Code!