2.x: marbles for Observable all, fromPublisher, zipArray

[akarnokd]

This PR adds a marble diagram to fromPublisher and updates the marbles of all and zipArray inside Observable.

The images can be seen in this comment of #5319.

[codecov]

Codecov Report

Merging #5740 into 2.x will increase coverage by 0.04%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##                2.x    #5740      +/-   ##
============================================
+ Coverage     96.24%   96.29%   +0.04%     
- Complexity     5827     5830       +3     
============================================
  Files           634      634              
  Lines         41615    41615              
  Branches       5761     5761              
============================================
+ Hits          40054    40073      +19     
+ Misses          626      611      -15     
+ Partials        935      931       -4

Impacted Files	Coverage Δ	Complexity Δ
src/main/java/io/reactivex/Observable.java	100% <ø> (ø)	509 <0> (ø)	⬇️
...ernal/operators/flowable/FlowableFlatMapMaybe.java	88.88% <0%> (-4.35%)	2% <0%> (ø)
...rnal/operators/observable/ObservableObserveOn.java	97.95% <0%> (-2.05%)	3% <0%> (ø)
.../internal/disposables/ListCompositeDisposable.java	98% <0%> (-2%)	34% <0%> (-1%)
...internal/operators/completable/CompletableAmb.java	98.3% <0%> (-1.7%)	11% <0%> (ø)
...a/io/reactivex/internal/util/QueueDrainHelper.java	58.86% <0%> (-1.42%)	31% <0%> (-1%)
...x/internal/operators/flowable/FlowablePublish.java	94.27% <0%> (-1.33%)	11% <0%> (+1%)
...ex/internal/operators/flowable/FlowableCreate.java	96.77% <0%> (-0.97%)	6% <0%> (ø)
...tors/observable/ObservableSequenceEqualSingle.java	98.29% <0%> (-0.86%)	3% <0%> (ø)
...nternal/operators/observable/ObservableCreate.java	98.29% <0%> (-0.86%)	2% <0%> (ø)
... and 18 more

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