Audit of timer functions for Windows compatibility

[jmtayloruk]

On Windows, time.time() has dreadful granularity (defaults to 1/60s). This led to divide by zero errors when computing fps in optical_gater_server. I have worked around that by switching to time.perf_counter(), which is apparently the gold standard for cross-platform timing of this sort. But we should go through other uses of time.time() and decide whether to switch them over to time.perf_counter() as well