[later phase] [PP-N] Optimize real-time XB previews of a formatted text field used as a DynamicPropSource by inspecting filter plugin types

Overview

This work only becomes relevant after 📌 Implement endpoint for realtime preview Active is a reality.
Follow-up for 📌 `StringSemanticsConstraint::MARKUP`: agree how SDC prop JSON schema can convey it should be markup, and Needs review .

Most text formats use multiple filter plugins, not just the filter_html filter. They virtually all require a round trip to the server: filter_image_lazy_load, filter_caption etc. all are TYPE_TRANSFORM_REVERSIBLE-type filters.

For these text formats, typing in the CKEditor 5 instance will require a round trip to the server to render a preview, so "true real-time updates will be impossible.

Note that all this is a solved problem: Drupal 8 core's Quick Edit module tackled exactly this. It's been ejected out of core, but lives on in contrib: https://drupal.org/project/quickedit. XB will be able to reuse the infrastructure it added, and will only need a subset of it.

Proposed resolution

TBD

User interface changes

TBD