Dropping some CompletableFuture allocations

[dfa1]

Hello @bbakerman @andimarek

just trying to improve the allocation rate (see the discussion in #3175).

There are 3 commits:

• first one is to drop TracingInstrumentation from BenchMark (to better understand the numbers from the profiler);
• second one is about to allocate less CompletableFuture in the Async class;
• third one is about removing the unused index parameter from Async CF factory functions: this will drop the allocations of java.lang.Integer.

On my machine, I get the following numbers.

Baseline:

Result "benchmark.BenchMark.benchMarkSimpleQueriesThroughput":
  62.101 ±(99.9%) 2.006 ops/s [Average]
  (min, avg, max) = (59.572, 62.101, 65.441), stdev = 1.877
  CI (99.9%): [60.095, 64.108] (assumes normal distribution)

With this PR:

Result "benchmark.BenchMark.benchMarkSimpleQueriesThroughput":
  65.212 ±(99.9%) 2.302 ops/s [Average]
  (min, avg, max) = (61.499, 65.212, 68.287), stdev = 2.154
  CI (99.9%): [62.910, 67.515] (assumes normal distribution)

I see also that the allocation rate of CompletableFuture is dropping a bit.

Please have a look :)

[bbakerman]

Thanks

[bbakerman]

This is a pretty good pattern for CFs that are really a static value - eg one that is completed and the same value