Both writing to perf.log frequently as well as GetTimestamp
aren't free and hurt performance particularly on slower systems
(which can have notably higher output to perf.log, further
amplifying the problem).
Therefore we make simulation perf logging opt-in.
Additionally, logging of the current tick and tick type
(local/net) is removed from debug.log, and some
remnant debug logging for kills and pips is removed
to keep performance-sensitive logging limited to
perf.log.
