2.x: Fix refCount() not resetting when cross-canceled

[akarnokd]

This PR fixes the issue with refCount not resetting the connection when the termination triggers cross-cancellation over it.

Fixes #6608

The fix is more involved than #6609 because how 2.x uses two publish() implementation internally due to bugfix #6505. The old/classic implementation does not fail #6608 but the newer implementation fails #6608. If the fix is applied unconditionally, the old/classic implementation fails an older unit test verifying an error allows reconnection. Therefore, the PR checks and applies the new code path only if refCount isn't talking to the classic publish implementation.

As a reminder #6609 for 3.x has a redesigned Connectable with a much more clearer reset semantics and thus the restructuring of the termination handling had no trouble passing the aforementioned error-allows-reconnect unit test.

[codecov]

Codecov Report

Merging #6629 into 2.x will decrease coverage by 0.04%.
The diff coverage is 95%.

@@             Coverage Diff              @@
##                2.x    #6629      +/-   ##
============================================
- Coverage     98.22%   98.18%   -0.05%     
- Complexity     6336     6342       +6     
============================================
  Files           677      677              
  Lines         45523    45545      +22     
  Branches       6330     6332       +2     
============================================
+ Hits          44717    44719       +2     
- Misses          257      261       +4     
- Partials        549      565      +16

Impacted Files	Coverage Δ	Complexity Δ
...ernal/operators/observable/ObservableRefCount.java	99.12% <95%> (-0.88%)	32 <5> (+4)
.../internal/operators/flowable/FlowableRefCount.java	99.13% <95%> (-0.87%)	32 <5> (+4)
...l/operators/observable/ObservableFlatMapMaybe.java	84.96% <0%> (-5.89%)	2% <0%> (ø)
...va/io/reactivex/internal/queue/SpscArrayQueue.java	97.61% <0%> (-2.39%)	22% <0%> (-1%)
...nternal/operators/parallel/ParallelSortedJoin.java	92.7% <0%> (-2.19%)	2% <0%> (ø)
...ernal/operators/flowable/FlowableFromIterable.java	94.11% <0%> (-2.14%)	5% <0%> (ø)
...nal/operators/observable/ObservablePublishAlt.java	96.26% <0%> (-1.87%)	15% <0%> (-1%)
...perators/mixed/ObservableConcatMapCompletable.java	98.49% <0%> (-1.51%)	3% <0%> (ø)
...a/io/reactivex/internal/util/QueueDrainHelper.java	98.61% <0%> (-1.39%)	57% <0%> (-1%)
...perators/mixed/ObservableSwitchMapCompletable.java	98.94% <0%> (-1.06%)	3% <0%> (ø)
... and 21 more

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