Support tcpdump pcap filters for stream identification

[SPYFF]

Extend IPv6 flowlabel based stream identification with generic, tcpdump filter expression support.

• Use libpcap to compile string to cBPF bytecode
• Pass the compiled cBPF filter to kernel with a BPF map
• Implement a cBPF interpreter in eBPF
• The interpreter execute the cBPF filter on packet received in XDP