Io Scheduler, Scheduled worker release (v2.x)

[sgc-code]

This is the same change as #7160 but targeting the 2.x branch
Related to issue #7153

[codecov]

Codecov Report

Merging #7162 (c2145a0) into 2.x (947b05f) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##                2.x    #7162      +/-   ##
============================================
- Coverage     98.24%   98.24%   -0.01%     
+ Complexity     6347     6346       -1     
============================================
  Files           677      677              
  Lines         45548    45553       +5     
  Branches       6341     6342       +1     
============================================
+ Hits          44748    44752       +4     
+ Misses          251      249       -2     
- Partials        549      552       +3     

Impacted Files	Coverage Δ	Complexity Δ
.../main/java/io/reactivex/schedulers/Schedulers.java	100.00% <ø> (ø)	11.00 <0.00> (ø)
.../io/reactivex/internal/schedulers/IoScheduler.java	89.89% <100.00%> (+0.53%)	9.00 <0.00> (ø)
...nal/operators/observable/ObservablePublishAlt.java	92.52% <0.00%> (-1.87%)	14.00% <0.00%> (ø%)
...tivex/internal/operators/single/SingleTimeout.java	98.33% <0.00%> (-1.67%)	2.00% <0.00%> (ø%)
...operators/observable/ObservableMergeWithMaybe.java	99.10% <0.00%> (-0.90%)	2.00% <0.00%> (ø%)
...nternal/operators/observable/ObservableCreate.java	97.43% <0.00%> (-0.86%)	2.00% <0.00%> (ø%)
...al/operators/observable/ObservableWindowTimed.java	90.42% <0.00%> (-0.85%)	4.00% <0.00%> (ø%)
.../operators/maybe/MaybeFlatMapIterableFlowable.java	97.54% <0.00%> (-0.82%)	2.00% <0.00%> (ø%)
...ex/internal/operators/flowable/FlowableCreate.java	96.77% <0.00%> (-0.65%)	6.00% <0.00%> (ø%)
.../operators/observable/ObservableCombineLatest.java	96.31% <0.00%> (-0.62%)	6.00% <0.00%> (ø%)
... and 14 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 947b05f...c2145a0. Read the comment docs.