bench: measure total/init/dispatch/cleanup times

* Add finer-grained measurements to the million_timers benchmark.
  Before this commit it only measured the total running time.

* Bump the number of inserted timers from 1M to 10M.  With one million
  timers, it finishes too quickly to get useful profiling data out of
  it with perf or oprofile.  The name of the benchmark is now a lie but
  such is life.