ensure aliased prefetches return correct segment key (#69850)
When returning an aliased prefetch, we need to make sure the final tree
that is produced contains the final searchParams, as otherwise the
router might not properly re-key the component to reflect the changed
search value. This moves the existing util that handled appending
`searchParams` to the `__PAGE__` segment into the shared segment
helpers. On the client, when we detect that we returned an aliased
prefetch, we update the segment key with the "final" data by calling
this helper with the final searchParams.
This also fixes a missing `aliased` detection in the case where we do
find an entry as it's possible the entry matches the path, but not the
search. It wasn’t sufficient to only do this for full prefetches because
while auto prefetches won’t return the CacheNode data, it will return a
tree, so we need to make sure the tree contains the right params.
Fixes #69847
