2.x: Fix Flowable.take to route post-cancel errors to RxJavaPlugins.onError

[akarnokd]

This PR makes sure errors emitted by the upstream just after the Flowable.take has received the specified amount of items get routed to RxJavaPlugins.onError.

Observable.take() and Flowable.limit() were already doing this. Added unit tests to verify the behavior across the board.

[codecov]

Codecov Report

Merging #5978 into 2.x will increase coverage by 0.03%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##               2.x    #5978      +/-   ##
===========================================
+ Coverage     98.2%   98.23%   +0.03%     
+ Complexity    6052     6049       -3     
===========================================
  Files          656      656              
  Lines        44077    44078       +1     
  Branches      6118     6118              
===========================================
+ Hits         43287    43302      +15     
+ Misses         243      232      -11     
+ Partials       547      544       -3

Impacted Files	Coverage Δ	Complexity Δ
...ivex/internal/operators/flowable/FlowableTake.java	100% <100%> (ø)	2 <0> (ø)	⬇️
.../operators/flowable/FlowableBlockingSubscribe.java	91.89% <0%> (-5.41%)	9% <0%> (-1%)
...activex/internal/observers/QueueDrainObserver.java	97.43% <0%> (-2.57%)	21% <0%> (-1%)
...perators/single/SingleFlatMapIterableFlowable.java	95.83% <0%> (-2.5%)	2% <0%> (ø)
...nternal/operators/observable/ObservableWindow.java	98% <0%> (-2%)	3% <0%> (ø)
...activex/internal/schedulers/ScheduledRunnable.java	98.07% <0%> (-1.93%)	29% <0%> (-1%)
...java/io/reactivex/processors/UnicastProcessor.java	98.8% <0%> (-1.2%)	67% <0%> (-1%)
...ternal/operators/completable/CompletableMerge.java	97.61% <0%> (-1.2%)	2% <0%> (ø)
...perators/observable/ObservableMergeWithSingle.java	99.06% <0%> (-0.94%)	2% <0%> (ø)
.../operators/mixed/FlowableConcatMapCompletable.java	99.14% <0%> (-0.86%)	2% <0%> (ø)
... and 21 more

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[vanniktech]

ObservableLimitTest already has this unit test?

[akarnokd]

Not this specific one.

[vanniktech]

If this is tested in a different test then fine, otherwise it might make sense to also add it.

[akarnokd]

There is no ObservableLimit.

[vanniktech]

Alright. Then merge.