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: Change egress/PACKET_IN processes to a method

When a sending process works only one time as before, a receiving process is performed as a method.
When a sending process works continuously, a receiving process is performed as a thread.
sw test tool: Change table-miss processes to a method

When a sending process works only one time as before, a table-miss checking process is performed as a method.
When a sending process works continuously, a table-miss checking process is performed as a thread.
sw test tool: Enable sending packets continuously