Support UDP connections

[kfirtoledo]

Support UDP connection for different application use cases. Another future solution could use H3/QUIC allowing both UDP and TCP to be transported between MVGs. An optional short-term solution might be to mark UDP sessions as such during establishment, still using TCP as the transport between the gateways. Then gateways encode/decode each UDP data as between gateways, ending with UDP <=> TCP <=> UDP end to end.