3.x: Fix mergeWith not cancelling the other source if the main errors

[akarnokd]

The mergeWith implementations' onError (called by the main source) cancelled the main source instead of cancelling the other source. This mistake affects all 2 x 3 overloads of the operator.

Fixes #6597

[codecov]

Codecov Report

Merging #6598 into 3.x will decrease coverage by 0.02%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##                3.x   #6598      +/-   ##
===========================================
- Coverage     98.22%   98.2%   -0.03%     
+ Complexity     6185    6184       -1     
===========================================
  Files           678     678              
  Lines         44908   44908              
  Branches       6214    6214              
===========================================
- Hits          44111   44100      -11     
- Misses          266     272       +6     
- Partials        531     536       +5

Impacted Files	Coverage Δ	Complexity Δ
...nal/operators/flowable/FlowableMergeWithMaybe.java	100% <100%> (ø)	2 <0> (ø)	⬇️
...erators/flowable/FlowableMergeWithCompletable.java	100% <100%> (ø)	2 <0> (ø)	⬇️
...al/operators/flowable/FlowableMergeWithSingle.java	100% <100%> (ø)	2 <0> (ø)	⬇️
...operators/observable/ObservableMergeWithMaybe.java	100% <100%> (ø)	2 <0> (ø)	⬇️
...perators/observable/ObservableMergeWithSingle.java	99.06% <100%> (-0.94%)	2 <0> (ø)
...ors/observable/ObservableMergeWithCompletable.java	100% <100%> (ø)	2 <0> (ø)	⬇️
...l/operators/observable/ObservableFlatMapMaybe.java	89.54% <0%> (-3.93%)	2% <0%> (ø)
...activex/internal/observers/QueueDrainObserver.java	97.43% <0%> (-2.57%)	21% <0%> (-1%)
...ternal/operators/completable/CompletableMerge.java	96.42% <0%> (-2.39%)	2% <0%> (ø)
...ava/io/reactivex/processors/BehaviorProcessor.java	96.58% <0%> (-1.47%)	51% <0%> (+1%)
... and 16 more

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[Mikey-Burns]

Minor typo in some of the test method names. The rest of the fix looks great.