3.x: Rename workflow tasks

[benjamintboyle]

Change 'build' tasks name to Build RxJava. Update Javadoc task names.

[codecov]

Codecov Report

Merging #7262 (6db8327) into 3.x (2f4815d) will decrease coverage by 0.02%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##                3.x    #7262      +/-   ##
============================================
- Coverage     99.55%   99.52%   -0.03%     
+ Complexity     6759     6757       -2     
============================================
  Files           747      747              
  Lines         47391    47391              
  Branches       6382     6382              
============================================
- Hits          47179    47167      -12     
- Misses           93      101       +8     
- Partials        119      123       +4     

Impacted Files	Coverage Δ	Complexity Δ
...observable/ObservableWindowSubscribeIntercept.java	87.50% <0.00%> (-12.50%)	4.00% <0.00%> (-1.00%)
...l/operators/observable/ObservableFlatMapMaybe.java	94.36% <0.00%> (-2.82%)	2.00% <0.00%> (ø%)
...eactivex/rxjava3/processors/BehaviorProcessor.java	97.48% <0.00%> (-2.52%)	50.00% <0.00%> (ø%)
...va/io/reactivex/rxjava3/subjects/AsyncSubject.java	97.87% <0.00%> (-2.13%)	44.00% <0.00%> (-1.00%)
...ernal/operators/flowable/FlowableFlatMapMaybe.java	96.89% <0.00%> (-1.56%)	2.00% <0.00%> (ø%)
...internal/operators/flowable/FlowableSwitchMap.java	98.58% <0.00%> (-1.42%)	3.00% <0.00%> (ø%)
...3/internal/operators/flowable/FlowablePublish.java	99.00% <0.00%> (-1.00%)	18.00% <0.00%> (ø%)
...operators/observable/ObservableMergeWithMaybe.java	99.09% <0.00%> (-0.91%)	2.00% <0.00%> (ø%)
.../operators/maybe/MaybeFlatMapIterableFlowable.java	99.18% <0.00%> (-0.82%)	2.00% <0.00%> (ø%)
...3/internal/operators/observable/ObservableZip.java	99.31% <0.00%> (-0.69%)	6.00% <0.00%> (ø%)
... and 9 more

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