Should switching text editors retain image upload settings?

Problem/Motivation

Discovered while working on #3245320: Automatic upgrade path always disables image uploads — in the UI.

Root cause:
editor_form_filter_admin_format_editor_configure() does

    elseif (empty($editor) || $editor_value !== $editor->getEditor()) {
      $format = $form_state->getFormObject()->getEntity();
      $editor = Editor::create([
          'format' => $format->isNew() ? NULL : $format->id(),
        'editor' => $editor_value,
      ]);
      $form_state->set('editor', $editor);
    }

It's that second condition that allows entering this branch that is true when switching the text editor. While text-editor specific settings cannot be carried over, image upload settings can be, because they're embedded in the Editor config entity at the top-level, and they even have an API interface: \Drupal\editor\EditorInterface::getImageUploadSettings() + \Drupal\editor\EditorInterface::setImageUploadSettings().

Steps to reproduce

Switch the default Basic HTML text format to use CKEditor 5 and observe the image uploads setting getting turned off.

Proposed resolution

Carry over image upload settings when switching text editor.

Remaining tasks

User interface changes

None.

API changes

None.

Data model changes

None.

Release notes snippet

None.