3.x: Add onErrorComplete to Flowable, Observable and Single

[akarnokd]

Add the onErrorComplete() and onErrorComplete(Predicate) operators to the remaining base classes.

Also created the missing marble for Maybe.onErrorComplete + 1.

Related #6852, #5806

[codecov]

Codecov Report

Merging #6867 into 3.x will decrease coverage by 0.02%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##                3.x    #6867      +/-   ##
============================================
- Coverage     98.24%   98.21%   -0.03%     
- Complexity     6417     6430      +13     
============================================
  Files           716      719       +3     
  Lines         46668    46744      +76     
  Branches       6397     6401       +4     
============================================
+ Hits          45847    45911      +64     
- Misses          295      309      +14     
+ Partials        526      524       -2

Impacted Files	Coverage Δ	Complexity Δ
src/main/java/io/reactivex/rxjava3/core/Maybe.java	100% <ø> (ø)	185 <0> (ø)	⬇️
...rc/main/java/io/reactivex/rxjava3/core/Single.java	100% <100%> (ø)	157 <2> (+2)	⬆️
...al/operators/flowable/FlowableOnErrorComplete.java	100% <100%> (ø)	2 <2> (?)
.../main/java/io/reactivex/rxjava3/core/Flowable.java	100% <100%> (ø)	578 <2> (+2)	⬆️
...perators/observable/ObservableOnErrorComplete.java	100% <100%> (ø)	2 <2> (?)
...ain/java/io/reactivex/rxjava3/core/Observable.java	100% <100%> (ø)	553 <2> (+2)	⬆️
...internal/operators/maybe/MaybeOnErrorComplete.java	100% <100%> (ø)	2 <1> (ø)	⬇️
...ternal/operators/single/SingleOnErrorComplete.java	100% <100%> (ø)	2 <2> (?)
...nternal/operators/observable/ObservableCreate.java	79.48% <0%> (-20.52%)	2% <0%> (ø)
...l/operators/observable/ObservableFlatMapMaybe.java	83.8% <0%> (-11.98%)	2% <0%> (ø)
... and 26 more

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