3.x: Rename zipIterable, remove zip(O(O)), adjust concatMapX arg order

[akarnokd]

• Rename zipIterable to zip
• Remove zip(ObservableSource<ObservableSource<T>>) and zip(Publisher<Publisher<T>>)
• Change the order of the tillTheEnd argument in concatMapDelayError and concatMapEagerDelayError to be consistent with other operators taking a boolean parameter before prefetch/maxConcurrency.

Related: #6610

[codecov]

Codecov Report

Merging #6638 into 3.x will decrease coverage by 0.04%.
The diff coverage is 100%.

@@ Coverage Diff @@ ## 3.x #6638 +/- ## ============================================ - Coverage 98.16% 98.12% -0.05%  + Complexity 6180 6174 -6  ============================================ Files 678 678 Lines 44795 44779 -16 Branches 6177 6177 ============================================ - Hits 43975 43940 -35  - Misses 279 291 +12  - Partials 541 548 +7

Impacted Files	Coverage Δ	Complexity Δ
...operators/observable/ObservableInternalHelper.java	100% <ø> (ø)	13 <0> (-1)	⬇️
...nal/operators/flowable/FlowableInternalHelper.java	100% <ø> (ø)	13 <0> (-1)	⬇️
.../main/java/io/reactivex/rxjava3/core/Flowable.java	100% <100%> (ø)	561 <4> (-1)	⬇️
...ain/java/io/reactivex/rxjava3/core/Observable.java	100% <100%> (ø)	537 <5> (-1)	⬇️
...l/operators/observable/ObservableFlatMapMaybe.java	86.8% <0%> (-9.03%)	2% <0%> (ø)
...nternal/operators/observable/ObservableToList.java	91.42% <0%> (-8.58%)	2% <0%> (-1%)
...tivex/rxjava3/disposables/CompositeDisposable.java	98.14% <0%> (-1.86%)	39% <0%> (-1%)
...ernal/operators/flowable/FlowableFromIterable.java	96.25% <0%> (-1.07%)	5% <0%> (ø)
...perators/observable/ObservableMergeWithSingle.java	99.07% <0%> (-0.93%)	2% <0%> (ø)
...perators/single/SingleFlatMapIterableFlowable.java	97.5% <0%> (-0.84%)	2% <0%> (ø)
... and 13 more

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