net: page_pool: support error injection

Because of caching / recycling using the general page allocation
failures to induce errors in page pool allocation is very hard.
Add direct error injection support to page_pool_alloc_pages().

Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/20240429144426.743476-2-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>