Changes to "Manually editable HTML tags" lost if form is submitted without triggering AJAX

Problem/Motivation

It seems like changes to "Manually editable HTML tags" field are lost if form is submitted without triggering AJAX.

Steps to reproduce

1. Create text format using CKEditor 5
2. Enable Source plugin
3. Enable the "Limit allowed HTML tags and correct faulty HTML" filter
4. Add <div data-foo> to "Manually editable HTML tags"
5. Press "Save" without clicking anywhere else on the page
6. Visit text format and confirm that "Manually editable HTML tags" field is empty

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet