Allow `CodeEditorControl` to be instantiated with a `editor_settings` param which is merged with `wp.codeEditor.defaultSettings`.
Also:
* Turn redundant "CSS Code" control label into screen reader text for Additional CSS.
* Remove `code-editor` as script dependency for `custom-html-widgets` since enqueueing is determined by `wp_enqueue_code_editor()`.
* Remove useless exporting of `code_type` param to JS in `WP_Customize_Code_Editor_Control`.
* Add `disabled` class to Custom HTML widget's Save button when linting errors are present.
* Remove redundant `span` inside CodeEditorControl's `label`.
See #41897, #12423, #41872.
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