3.x: Add missing marble diagams to Single

[akarnokd]

Add (hopefully) all remaining missing marble diagrams to Single.

Resolves #5788

[codecov]

Codecov Report

Merging #6668 into 3.x will increase coverage by 0.01%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##               3.x    #6668      +/-   ##
===========================================
+ Coverage     98.1%   98.12%   +0.01%     
  Complexity    6187     6187              
===========================================
  Files          677      677              
  Lines        44682    44682              
  Branches      6169     6169              
===========================================
+ Hits         43837    43843       +6     
+ Misses         303      299       -4     
+ Partials       542      540       -2

Impacted Files	Coverage Δ	Complexity Δ
...rc/main/java/io/reactivex/rxjava3/core/Single.java	100% <ø> (ø)	148 <0> (ø)	⬇️
.../operators/observable/ObservableFlatMapSingle.java	88.09% <0%> (-6.35%)	2% <0%> (ø)
...rxjava3/internal/observers/QueueDrainObserver.java	97.43% <0%> (-2.57%)	21% <0%> (-1%)
...ernal/operators/flowable/FlowableFlatMapMaybe.java	91.14% <0%> (-2.09%)	2% <0%> (ø)
...tivex/rxjava3/disposables/CompositeDisposable.java	98.14% <0%> (-1.86%)	39% <0%> (-1%)
...ctivex/rxjava3/internal/util/QueueDrainHelper.java	98.61% <0%> (-1.39%)	57% <0%> (-1%)
...reactivex/rxjava3/processors/UnicastProcessor.java	98.8% <0%> (-1.2%)	67% <0%> (-1%)
...a3/internal/operators/flowable/FlowableReplay.java	91.97% <0%> (-0.83%)	19% <0%> (ø)
...l/operators/observable/ObservableFlatMapMaybe.java	94.36% <0%> (-0.71%)	2% <0%> (ø)
...internal/operators/flowable/FlowableObserveOn.java	97.49% <0%> (+0.27%)	3% <0%> (ø)	⬇️
... and 13 more

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