Merge branch 'selftest-extend-tun-virtio-coverage-for-gso-over-udp-tunnel'

Xu Du says:

====================
selftest: Extend tun/virtio coverage for GSO over UDP tunnel

The design strategy is to extend the existing tun testing infrastructure
to support this new use-case, rather than introducing a new or parallel framework.
This allows for better integration and re-use of existing test logic.
====================

Link: https://patch.msgid.link/cover.1768979440.git.xudu@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>