cpu: Prune the stale TraceCPU

cpu: Prune the stale TraceCPU

This patch prunes the TraceCPU as the code is stale and the
functionality that it provided can now be achieved with the TrafficGen
using its trace playback mode.

The TraceCPU was able to play back pre-recorded memory traces of a few
different formats, and to achieve this level of flexibility with the
TrafficGen, use the util/encode_packet_trace (with suitable
modifications) to create a protobuf trace off-line.