Lift subtree data out of React tree (#58569)
Refactors createComponentTree to return a top-level tree of all the
subtree data in the entire response. Although we were already collecting
this data, it's passed to the client as a prop LayoutRouter, which means
it can only be unwrapped by rendering the React tree.
Instead, we will hoist all the subtree data (i.e. the React nodes that
represent the nested layouts) into a top-level object that can be
immediately unwrapped by the client when it processes the response.
Then, the client will use this tree to eagerly populate the cache nodes,
rather than waiting for the LayoutRouter to lazily populate the cache
during render, like we do today.
This PR does not implement the client-side changes yet; it only creates
the new data structure, which I've named CacheNodeSeedData. The rest
will come in subsequent PRs.
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Co-authored-by: Zack Tanner <zacktanner@gmail.com>
Co-authored-by: kodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>
