[incubator-kie-issues#780] DMN - Benchmarking InfixOpNode and InfixOperators

[gitgabrio]

Add InfixOpNode and InfixOpOperators specific benchmarks
Fixes apache/incubator-kie-issues#780

Continuation of #279 (closed due to branch renaming)

[mariofusco]

In my opinion using a Map as I did here, makes sense only as a context when evaluating an expression in integration, but not when benchmarking the Executors in isolation as you're doing. Also accessing the map in the benchmarking method has a cost that you may want to avoid, because it is just noise and not the thing that you want to measure. You could obtain the same result using an Object[] instead of a Map so that in the benchmarking method instead of having

    @Benchmark
    public Object evaluate() {
        return executor.evaluate(map.get("a"), map.get("b"), ctx);
    }

you could just do

    @Benchmark
    public Object evaluate() {
        return executor.evaluate(array[0], array[1], ctx);
    }

Also I suggest to add more benchmarks parsing and evaluating complete expression in the same style of the one in my comment that I linked above (but this could be eventually done with another PR as well).