2.x: add/update Observable marbles 11/28

[akarnokd]

This PR adds or updates mable diagrams of Observable:

• blockingFirst
• blockingFirst with default
• toFuture
• blockingSubscribe no arguments
• blockingSubscribe with 1 argument
• blockingSubscribe with 2 arguments
• blockingSubscribe with 3 arguments
• collectInto
• doOnComplete
• doOnError
• doOnLifecycle
• doOnNext
• doOnDispose

Related #5319: comment.

[codecov]

Codecov Report

Merging #5745 into 2.x will decrease coverage by <.01%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##                2.x    #5745      +/-   ##
============================================
- Coverage     96.25%   96.25%   -0.01%     
- Complexity     5833     5837       +4     
============================================
  Files           634      634              
  Lines         41644    41644              
  Branches       5768     5768              
============================================
- Hits          40086    40083       -3     
- Misses          625      627       +2     
- Partials        933      934       +1

Impacted Files	Coverage Δ	Complexity Δ
src/main/java/io/reactivex/Observable.java	100% <ø> (ø)	509 <0> (ø)	⬇️
...l/operators/observable/ObservableFlatMapMaybe.java	84.96% <0%> (-7.19%)	2% <0%> (ø)
.../operators/completable/CompletableConcatArray.java	93.75% <0%> (-6.25%)	2% <0%> (ø)
...erators/completable/CompletableConcatIterable.java	95.91% <0%> (-4.09%)	2% <0%> (ø)
.../operators/observable/ObservableFlatMapSingle.java	90.29% <0%> (-3.74%)	2% <0%> (ø)
...nternal/operators/parallel/ParallelSortedJoin.java	92.75% <0%> (-2.18%)	2% <0%> (ø)
...ex/internal/subscribers/InnerQueuedSubscriber.java	96.07% <0%> (-1.97%)	18% <0%> (-1%)
.../io/reactivex/disposables/CompositeDisposable.java	97.24% <0%> (-1.84%)	39% <0%> (-1%)
...vex/internal/operators/parallel/ParallelRunOn.java	95.65% <0%> (-1.45%)	8% <0%> (ø)
...vex/internal/operators/flowable/FlowableCache.java	93.95% <0%> (-1.35%)	7% <0%> (ø)
... and 22 more

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[ZacSweers]

The different colored stars in doOnLifecycle weren't obvious to me, but the rest seems good