mm: remove page_idle and page_young wrappers

All users have now been converted to the folio equivalents, so remove the
page wrappers.

Link: https://lkml.kernel.org/r/20240402201252.917342-4-willy@infradead.org


Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>