Fix issue #79 (negative duration/elapsed time)

[oswaldobapvicjr]

This PR solves the bug #79.

I could reproduce the trouble creating a MonitoredRunnable that executes a simple and fast runnable 1 million times (the average duration for the SYSTEM_TIME counter was 0.000002312 seconds).

During the analysis, I realized that, in some (frequent) cases, the nanoseconds after the operation were populated with an amount that was lower than the value retrieved before the operation, due to a known accuracy issue inside JDK's ThreadMXBean.

According to the JDK 17 Javadoc: "The CPU time provided is of nanoseconds precision but not necessarily nanoseconds accuracy" (https://docs.oracle.com/en/java/javase/17/docs/api/java.management/java/lang/management/ThreadMXBean.html).

So, to avoid the negative elapsed time, I implemented the following fixes:

• The Counter.elapsedTimeNanos() was modified to return zero (instead of -1) when the time retrieved after the operation is lower than the one retrieved before the operation
• The Duration class now also allows negative amounts, to prevent the issue from happening in another situation (for example, if CPU time is not supported by the JVM)

The fix was validated with JUnit and a new stress test method at the PerformetricsTestDrive class.

✅ The fix will be released in Performetrics version 2.5.2.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (1c595bf) to head (4306f58).

Additional details and impacted files

@@             Coverage Diff             @@
##              master       #80   +/-   ##
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  Coverage     100.00%   100.00%           
+ Complexity       326       325    -1     
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  Files             21        21           
  Lines            831       829    -2     
  Branches          34        34           
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- Hits             831       829    -2     

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