next.js

ddffb8d9 - Fix PPR navigations & revert `layerAssets` property from FlightData (#67435)

Fix PPR navigations & revert `layerAssets` property from FlightData (#67435) This PR was originally intended to ensure style/script tags were always rendered for all visible parallel routes, as before only the "first" child was rendered, similar to `head`. However, it caused a regression in PPR navigations, as the pending task on the `layerAssets` CacheNode meant that the `useDeferredValue` call in `layout-router` wouldn't be able to immediately switch to the prefetched RSC payload, as it was blocked by the dynamic response. Since `rsc` and `layerAssets` are both created by the same thing, this stack of PRs rewinds some of that work to combine them. This PR only reverts the previous implementation, and adds a test for the PPR navigation case that was failing. **Note: While I've split these PRs out for readability, this should land with #67436 as this PR by itself does not restore the CSS behavior that was fixed in the original implementation.**