bpf: add tcx support

JIRA: https://issues.redhat.com/browse/RHEL-28590
Depends: !3841 (merged)
Tested: bpf tc selftests pass, manual tests that the tcx hooks work as
expected.

Add the new tcx hook for bpf. It attaches at a similar place as the tc
hook but has several advantages: it is based on the new multi prog
infrastructure in the kernel to allow adding multiple bpf programs at
the same hook; it follows the link semantics most other bpf hooks use
which gives applications better control over the lifecycle of the bpf
program; and tcx does not require a qdisc making the setup simpler.

Signed-off-by: Felix Maurer fmaurer@redhat.com