Need consider use case on multiple connections for 2 device

[jyao1]

SPDM 1.2 spec define:
2 device may only have one physical channel, but they can have multiple virtual SPDM connections.
Each virtual SPDM connection should have one dedicate spdm_context.

spdm-dump can consider such scenario. Multiple connection (spdm_context) in one pcap.