Paragraphs 2.x [#3464319]

Problem/Motivation

This is an issue to map out a rough plan for a Paragraphs 2.x release. No timeline, and no guarantees that any of this is going to make it.

Similar to core, 2.x is less about new features, it's more about dealing with technical dept and internal changes.

Remove legacy widget
Move migrate stuff to a separate project. Maintenance of that code required a fair amount of time, for example latest with D11 compatibility. Looking for volunteers to adopt such a new project.
Convert behavior settings storage from serialized strings to json
Adopt layouts and styles from the paragraphs_collection project. Clearly the two most useful features of that projects and they have served us well for quite a few years now.
Adopt recipes, replacing the demo module, and possibly also most or all remaining bits of the paragraphs_collection project. One thing to note is that collection isn't only configuration, but also a number of plugins.

To be defined: Possibly some bigger changes from existing issues that I've so far been holding back, e.g. improvements around the parent/revision situation, like a parent revision field.