Take a long hard look at the benchmarks and make some of them JMH

[Palmr]

There are many classes and tests under the "perf" sourceset. Not sure what all of these do, if they're relevant etc.

There is currently no way to track performance of the Disruptor in CI. Using some standard tools like JMH we can write benchmarks which output results in a standard way for tracking & display.

We also have a lot of performance related code in the code base which doesn't appear to have any directly linked benchmarks proving it's a faster way of doing things. Performance code is typically harder to read and needs to justify its existence with some form of benchmark.

[Palmr]

Since #314 we now have JMH benchmarks in the code. Need to add more and consider where we can find a stable environment to run them and record results.