Support measuring the cost of hooks and events

[vweevers]

Ref Level/abstract-level#45

[vweevers]

To make it easier to compare results, I added a way to collect ops/sec and print it as a table. Only for the put benchmark, to start:

$ level-bench.js run put ..\memory-level
$ level-bench.js run put ..\memory-level --events [ --put=1 ]
$ level-bench.js run put ..\memory-level-hooks --hooks [ --prewrite=1 ]
$ ...
$ level-bench plot put
benchmark put on memory-level@1.0.0 win32 x64
node@16.9.1 n=1M concurrency=4 valueSize=100B keys=random values=random
1 memory-level#hooks 36588 ops/s ±8.51% fastest
2 memory-level#main 35837 ops/s ±8.12% +1.70%
3 memory-level#hooks hooks.prewrite=1 35286 ops/s ±6.51% +1.75%
4 memory-level#main events.put=1 35508 ops/s ±7.47% +2.01%
5 memory-level#hooks events.write=1 34692 ops/s ±6.83% +3.69%
6 memory-level#hooks hooks.prewrite=100 34302 ops/s ±8.28% +6.05%