Reduce function indirection in histogram.js for easier debugging

[jdmarshall]

Also add missing benchmarks for startTimer(), since I'm mucking about in its innards.

In theory removing call() for arrow functions or straight calls improves performance, but I've never managed a benchmark that proves it. This change also reduces closure creation but GC is also difficult to benchmark. Make enough of these changes however and you can get yourself a little teeny tiny notch in your telemetry data that proves you did something (I think I clocked my test case at about .8%, because the calls were slow and so that added up to 5+ms).

So these are officially just about improving single step debugging.

One of the places where Prometheus can outshine OpenTelemetry is in trying to figure out why your metrics are confusing/missing/garbled. If you've ever tried to single-step through OTEL it's a maze of twisty little passages, all the same. prom-client has a fairly straightforward architecture and thus is already much better in this regard but I'm interested in making tools that need to 'just work' more approachable.

[SimenB]

makes sense to me 👍

mind addressing the ESLint warnings?

(I'm not an admin on this repo, so unable to have the actions trigger for first contributions 😅 since a bunch of your other changes have landed tho, it shouldn't be an issues once you push again)

[zbjornson]

Looks good!