supports AF_XDP socket diagnosis

[thediveo]

• dumps the diagnosis data of all sockets of type AF_XDP in the current network namespace.
• dumps the diagnosis data of only a single socket that matches a specific inode number an/or socket cookie. Now, while the XDP socket diagnosis request allows for specifying a inode number and socket cookie this information doesn't seem to be used in the Linux kernel xsk_diag.c implementation anywhere and tests show that no filtering takes place.

Supplying tests is rather complex in the case of AF_XDP sockets and while I have tests, these pull in lots of other code because of the long-winded way these sockets need to be properly set up and rely on the Ginkgo/Gomega TDD framework in order to reduce lots of boilerplate, so I'm refraining from polluting the netlink module.

[aboch]

@thediveo please resolve the conflicts

[thediveo]

@aboch any idea why ...

=== RUN   TestSocketXDPGetInfo
    socket_xdp_linux_test.go:30: no such file or directory
--- FAIL: TestSocketXDPGetInfo (0.00s)

...fails on the Github runner, but succeeds on both a Ubuntu 24.04 (kernel 6.8) and 22.04LTS (kernel 5.15.0)?

[thediveo]

@aboch skipping XDP socket diagnosis test if kernel reports ENOENT, thus lacking XSK diagnosis.

[aboch]

please squash the two commits into one

[thediveo]

@aboch done

[thediveo]

any issues, or can this be please merged?