net: page_pool: support dumping pps of a specific ifindex via Netlink

NIPA tries to make sure that HW tests don't modify system state.
It saves the state of page pools, too. Now that I write this commit
message I realize that this is impractical since page pool IDs and
state will get legitimately changed by the tests. But I already
spent a couple of hours implementing the filtering, so..

Link: https://patch.msgid.link/20260506034821.1710113-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>