New benchmark modes

[Nitsan Wakart]

Hi,I would like to suggest/have a few new benchmark modes:1. Histogram: This is similar to SampleTime, but I would like to always measure. I realize that pre/post timestamps may not be a good idea for small workloads, and that nanoTime doesn't scale. This is so similar to Sample that one could argue for making this a configurable mode of SampleTime (e.g add controls for sample probability and max samples per ms), I'd be happy with that solution too.I would also like to have the timing data recorded in HdrHistogram. Not that there's anything wrong with the JMH histogram, they are very similar, but I'd like to serialize the data in the HdrHistogram format to support downstream processing with other tools. Supporting a pluggable sink for measurements is an integration challenge, not sure how best to allow for that or if there's a game plan already in the wings.2. Fixed rate + Histogram (response+service): JMH currently supports only an all-out measurement mode. I'd like to have a fixed operation rate mode where a given operation is executed X times a second. The measurement collected is both for response time(end time - scheduled start time) and service time(end time - actual start time). This to avoid coordinated omission in measurement.I realize benchmark modes and the code generation they require is fundamental to the workings of JMH, I'm not sure this part can be opened up to extension such that the above benchmark modes can be added as extensions rather than included in the JMH codebase. If you see a clear path to openning up JMH for extension that way it might be easier to allow users more freedom to experiment with custom benchmark modes as above while retaining the benefits of the rest of JMH.I'm happy to contribute code to of enable the above.Thanks,Nitsan