3.x: Allow Single.zip and Maybe.zip result to be garbage collected

[zireael-0]

Resolves #7195

[akarnokd]

Please adjust the PR for both classes.

[zireael-0]

@akarnokd Sorry, hit re-review accidentally 🙈

[akarnokd]

Looks like I forgot about the case when the consumer retains the whole array reference, thus clearing it out can cause late errors.

Let's make values non-final and null it out instead as you originally suggested.

[akarnokd]

I committed a few changes to fix race conditions with the changes

[codecov]

Codecov Report

Merging #7196 (bcca53e) into 3.x (09b2b1b) will increase coverage by 0.03%.
The diff coverage is 95.00%.

@@             Coverage Diff              @@
##                3.x    #7196      +/-   ##
============================================
+ Coverage     99.49%   99.52%   +0.03%     
- Complexity     6752     6756       +4     
============================================
  Files           747      747              
  Lines         47350    47387      +37     
  Branches       6367     6384      +17     
============================================
+ Hits          47110    47163      +53     
+ Misses          112      101      -11     
+ Partials        128      123       -5     

Impacted Files	Coverage Δ	Complexity Δ
...ava3/internal/operators/single/SingleZipArray.java	98.68% <85.71%> (-1.32%)	6.00 <0.00> (ø)
...xjava3/internal/operators/maybe/MaybeZipArray.java	98.79% <87.50%> (-1.21%)	6.00 <0.00> (ø)
...main/java/io/reactivex/rxjava3/core/Scheduler.java	100.00% <100.00%> (ø)	16.00 <2.00> (ø)
...3/internal/operators/parallel/ParallelCollect.java	100.00% <100.00%> (ø)	7.00 <3.00> (ø)
...internal/operators/parallel/ParallelConcatMap.java	100.00% <100.00%> (ø)	5.00 <3.00> (ø)
...ternal/operators/parallel/ParallelDoOnNextTry.java	100.00% <100.00%> (ø)	6.00 <4.00> (ø)
...a3/internal/operators/parallel/ParallelFilter.java	100.00% <100.00%> (ø)	6.00 <4.00> (ø)
...internal/operators/parallel/ParallelFilterTry.java	100.00% <100.00%> (ø)	6.00 <4.00> (ø)
...3/internal/operators/parallel/ParallelFlatMap.java	100.00% <100.00%> (ø)	5.00 <3.00> (ø)
...al/operators/parallel/ParallelFlatMapIterable.java	100.00% <100.00%> (ø)	5.00 <3.00> (ø)
... and 29 more

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