This keeps track of the keys from parent Server Components that are
inherited down.

This is then prepended to the key of the terminal client element.

…keyed

If an element gets wrapped in a different server component then that has
a different keyPath context and the element might end up with a different
key.

So we don't use the deduping mechanism if we're already inside a
Server Component parent with a key or otherwise. Only the simple case
gets deduped.

The props of a client element are still deduped though if they're the
same instance.