soreuseport: BPF selection functional test

This program will build classic and extended BPF programs and
validate the socket selection logic when used with
SO_ATTACH_REUSEPORT_CBPF and SO_ATTACH_REUSEPORT_EBPF.

It also validates the re-programing flow and several edge cases.

Signed-off-by: Craig Gallek <kraig@google.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>