Spike: Explore adding configuration options to the tree item formatter to support alternate use-cases

Problem/Motivation

From #3462219-9: [META] Support alternative renderings of prop data added for the 'full' view mode such as for search indexing or newsletters →

Also thinking through the use-cases more above, I think they can be boiled down to three types. Each one assumes we are rendering a search index or newsletter or 'long teaser' view mode or any alternative rendering of the stuff we put in the full view mode.

1. Show everything in XB slots from the full view mode, except component type X

2. Show the first x deltas of specific component types from the XB slots on the full view mode. x deltas of x components. (testimonial, image gallery)

3. Show a few deltas of any component type, limited to a certain amount (long teaser)

Steps to reproduce

Proposed resolution

At present there's a primitive formatter for the XB `ComponentTreeitem` that essentially calls `::toRenderable` on the tree item. All the logic to take the tree data and convert it into a render array goes via the tree item.

In order to meet this use-case it would be simple enough to expand the formatter's settings to support the configuration options listed here i.e.

• component type disallow/allow list
• component type limits
• component delta limits

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet