SourceEditingRedundantTagsConstraintValidator logic handles attribute supersets incorrectly

Problem/Motivation

https://git.drupalcode.org/project/drupal/-/blob/9.4.x/core/modules/cked... triggers violation in the case where a plugin with supported elements superset is available. This could be incorrect in some cases. For example, a CKEditor 5 plugin could only convert <div> with data-foo attribute just by using the CKEditor 5 built in elementToElement conversion helper. The Drupal plugin would have to indicate this as <div data-foo>. The SourceEditingRedundantTagsConstraintValidator would then prevent the user from adding <div> to the source editing editable tags because it thinks that the plugin handling <div data-foo> would be able to handle <div>, even though the plugin would only be able to handle <div> with data-foo attribute.

We also have a pre-existing example of this in core; the codeBlock plugin. It is configured to support <pre> and <code class="language-*">, while it only supports <pre> elements that also contain a <code> element. We work around this by adding support for <pre> using GHS. This might be fine for core, but I assume we don't want all of the custom plugins have to consider all the subsets.

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet