sim: Remove broken AutoSerialize support from the event queue

sim: Remove broken AutoSerialize support from the event queue

Event auto-serialization no longer in use and has been broken ever
since the introduction of PDES support almost two years
ago. Additionally, serializing the individual event queues is
undesirable since it exposes the thread structure of the
simulator. What this means in practice is that the number of threads
in the simulator must be the same when taking a checkpoint and when
loading the checkpoint.

This changeset removes support for the AutoSerialize event flag and
the associated serialization code.