sw test tool: Enable parsing a new 'ingress' format

The format is for sending packets continuously.
sw test tool: Add support for sending packets continuously
sw test tool: Refactor packet sending processes

Methods of STATE_FLOW_MATCH_CHK and STATE_UNMATCH_PACKET_SEND have similar processes that send a packet.
This patch refactors this redundancy.
sw test tool: Rename STATE_UNMATCH_PKT_SEND to STATE_SEND_BARRIER

And rename _test_unmatch_packet_send() to _test_send_barrier().
sw test tool: Enable sending packets continuously