2.x: benchmark the new strict/interop mode

[akarnokd]

Benchmark the overhead of the strict/interop mode.

i5 6440HQ, Windows 10 x64, Java 8u121

The numbers are consistent with my expectations; this mobile processor is roughly equivalent to i7 4770 desktop where the cost model is: 1 atomic increment per item equals to roughly 130 Mops/s upper limit, 2 atomic increment per item is roughly 60 Mops/s upper limit. Since the interop mode requires at minimum two atomic increments, 54 Mops/s is a reasonable value to get.

[codecov]

Codecov Report

Merging #5115 into 2.x will decrease coverage by -0.03%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##                2.x    #5115      +/-   ##
============================================
- Coverage     95.15%   95.12%   -0.03%     
- Complexity     5561     5567       +6     
============================================
  Files           620      620              
  Lines         40011    40011              
  Branches       5632     5632              
============================================
- Hits          38072    38061      -11     
- Misses          920      939      +19     
+ Partials       1019     1011       -8

Impacted Files	Coverage Δ	Complexity Δ
...internal/disposables/ArrayCompositeDisposable.java	92.85% <ø> (-7.15%)	15% <ø> (-1%)
...ors/observable/ObservableSampleWithObservable.java	91.56% <ø> (-6.03%)	3% <ø> (ø)
...l/operators/observable/ObservableFlatMapMaybe.java	89.54% <ø> (-5.23%)	2% <ø> (ø)
...in/java/io/reactivex/subjects/BehaviorSubject.java	84.97% <ø> (-4.67%)	56% <ø> (+1%)
...ava/io/reactivex/processors/BehaviorProcessor.java	87.38% <ø> (-4.21%)	56% <ø> (+1%)
...io/reactivex/internal/util/BackpressureHelper.java	95.91% <ø> (-4.09%)	21% <ø> (-1%)
...ternal/operators/observable/ObservablePublish.java	91.89% <ø> (-3.61%)	10% <ø> (ø)
...al/operators/observable/ObservableSampleTimed.java	93.33% <ø> (-3.34%)	3% <ø> (ø)
.../operators/observable/ObservableFlatMapSingle.java	94.02% <ø> (-2.99%)	2% <ø> (ø)
...operators/observable/ObservableConcatMapEager.java	97.29% <ø> (-2.17%)	2% <ø> (ø)
... and 34 more

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[akarnokd]

Results with the updated benchmark, adding extra overhead by consuming CPU to see where the raw overhead decreases to a reasonably low value: