Component object backend props

[weaverryan]

Accomplishes 3) BACKEND: pass data (writable props) & props separately as live controller values from symfony#500

tl;dr

We now pass props (readonly LiveProp) and data (writable LiveProp) separately to the frontend. But then when we re-render, we still send back just one big array of BOTH mixed together.

Why do we need to differentiate between props and data on the frontend? It's for child components. When a parent re-renders, we will (it's another TODO on the PR) render the parent but with an EMPTY child element, except that we will include the props on that child element - e.g. this will come back from the Ajax request:

<div data-controller="live" ... data & props - all the normal attributes>
    I am a parent component

    <!-- here is the child - it's empty
    <div data-controller="live" data-live-props-value="{...}"></div>
</div>

This will allow us to grab the new props (which may have changed as a result of WHAT the parent component is passing into the child), override the props on the child, and then trigger the child to re-render with all the new stuff. What's important here is that, by differentiating props vs data, we can KEEP any modified "data" that the child has: only overriding the props that changed as a result of the parent component re-rendering.

[kbond]

Can more logic be moved to the new DehydratedComponent class?

[kbond]

LGTM!