Interactivity API: Add support for lazy-loaded derived state props

[DAreRodz]

This PR handles the server-side part to add support for "lazy" derived state props. From the trac ticket description:

There is a problem with derived state props when the store containing them is not loaded before hydration, which can happen with stores loaded asynchronously, e.g., @wordpress/interactivity-router, and also they have a PHP equivalent used for server-side rendering.

In that case, when those missing derived state props are evaluated, they will return undefined, and the directives subscribed to that value will replace the value generated on the server with the PHP function with undefined, effectively removing the HTML generated on the server.

The Interactivity API should be aware of which values were generated on the server via a PHP Closure (derived state props) and avoid replacing the directive's value on the client until a getter is available that can correctly recalculate it.

The way it works is by informing the iAPI runtime which Closures have been evaluated on the server, and serializing their paths into a data structure that is serialized along with the initial state and configuration.

There's also a special case with the data-wp-each-child directive. I should know if the corresponding parent data-wp-each directive is using a derived state prop to render the list.

Trac ticket: https://core.trac.wordpress.org/ticket/63898

Related Gutenberg issue: WordPress/gutenberg#70872
Related Gutenberg PR: WordPress/gutenberg#71125

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