selftests/net: Add queue leasing tests with netkit

selftests/net: Add queue leasing tests with netkit

Add extensive selftests for netkit queue leasing, using io_uring zero
copy test binary inside of a netns with netkit. This checks that memory
providers can be bound against virtual queues in a netkit within a
netns that are leasing from a physical netdev in the default netns.
Also add various test cases around corner cases for the queue creation
itself as well as queue info dumping and teardown in case of netkit in
device pair and single mode.

Signed-off-by: David Wei <dw@davidwei.uk>
Co-developed-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://patch.msgid.link/20260402231031.447597-15-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>