Improve notFound recovery in error pathway (#94037)
Effectively
Relands #93988
Reverts #92231
Prerendering the notFound loaderTree turns out to not be the correct
behavior in many cases. The original motivation of 92231 as to solve the
connection closed problem caused by statically prerendering an
incomplete HTTP event like notFound() when cacheComponents is enabled
because it would leave holes in the inlined flight data that never
resolved and led to reported errors on hydration.
This change now continues to fork the CC behavior of the error handler
but it treats the error page as a resumable page so fresh hydration data
is generated if it wasn't able to be entirely static.
This is good for correctness but it also means the page is not going to
statically prerender the notFound UI. This will be handled in a followup
---------
Co-authored-by: Hendrik Liebau <mail@hendrik-liebau.de>
