3.x: Introduce property rx3.scheduler.use-nanotime

[SergejIsbrecht]

Fixes #7154

[SergejIsbrecht]

@akarnokd ,

I got a problem, when I try to test the code, because when the class is loaded, one can not change set variable:

`private static final String DRIFT_USE_NANOTIME = "rx3.scheduler.drift-use-nanotime";

Resolution:

• no tests
• define a own test set, which tests the nanoTime use-case and configure this test-src-set to run each class in a new JVM
• find a Junit-runner which loads the test-classes via a own ClassLoader
• remove "final" for DRIFT_USE_NANOTIME and set it for testing, which might not be desirable, because it can be changed later.

What are your thoughts on this issue regarding testing?

[codecov]

Codecov Report

Merging #7169 (6cfd483) into 3.x (a99b2e0) will increase coverage by 0.05%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##                3.x    #7169      +/-   ##
============================================
+ Coverage     99.50%   99.56%   +0.05%     
- Complexity     6739     6742       +3     
============================================
  Files           747      747              
  Lines         47324    47328       +4     
  Branches       6360     6360              
============================================
+ Hits          47091    47120      +29     
+ Misses          108       94      -14     
+ Partials        125      114      -11     

Impacted Files	Coverage Δ	Complexity Δ
...va/io/reactivex/rxjava3/schedulers/Schedulers.java	100.00% <ø> (ø)	12.00 <0.00> (ø)
...main/java/io/reactivex/rxjava3/core/Scheduler.java	100.00% <100.00%> (ø)	16.00 <4.00> (+2.00)
...nternal/operators/parallel/ParallelReduceFull.java	93.06% <0.00%> (-1.99%)	2.00% <0.00%> (ø%)
...ternal/operators/flowable/FlowableWindowTimed.java	97.19% <0.00%> (-0.29%)	5.00% <0.00%> (ø%)
...3/internal/operators/flowable/FlowablePublish.java	99.00% <0.00%> (ø)	17.00% <0.00%> (-1.00%)
...ternal/operators/observable/ObservableFlatMap.java	97.87% <0.00%> (+0.35%)	3.00% <0.00%> (ø%)
...nternal/operators/observable/ObservableReplay.java	100.00% <0.00%> (+0.53%)	22.00% <0.00%> (ø%)
...ternal/operators/completable/CompletableMerge.java	98.64% <0.00%> (+1.35%)	2.00% <0.00%> (ø%)
...internal/operators/flowable/FlowableSwitchMap.java	100.00% <0.00%> (+1.41%)	3.00% <0.00%> (ø%)
.../operators/observable/ObservableFlatMapSingle.java	96.82% <0.00%> (+1.58%)	2.00% <0.00%> (ø%)
... and 5 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 a99b2e0...6cfd483. Read the comment docs.

[akarnokd]

Since this affects now(), let's call the property just rx3.scheduler.use-nanotime.

[SergejIsbrecht]

@akarnokd , I'll changed the commit message as-well, to match the new property name.

[akarnokd]

No need for that.