Colocate data fetching; use proper server components

[unstubbable]

Performing all image search requests upfront, before rendering any image components, wasn't really in line with how server components should work. This approach was initially chosen to obtain a single function AI state that contains data from all searches.

With the introduction of the onDataFetched prop, we can achieve the same outcome while moving data fetching directly into the server components, where it belongs.

This change also makes it easier to add loading skeletons later on.

The approach does have the downside that we need to follow this kind of awkward rendering approach:

• map over searches to create pairs of elements and their data promises
• yield the elements as part of the "final UI" (but suspended)
• await all the data from the child components, and put it into the AI state
• return the final UI

[unstubbable]

This only works in development mode for some reason. In production mode (also locally), the intermediate UI is removed in the client, when the final RSC rows have been processed.