Stabilize iterators, fix StackOverflowError, and clean up legacy dependencies

[ismailtsdln]

Summary of Changes

1. Fixed StackOverflowError in MetricAgeOffIterator (#150)

The seekIfNecessary method previously used recursion to skip aged-off data.
In scenarios with a large number of skipped keys, this caused a StackOverflowError.

The method was refactored to use a robust while loop instead of recursion.

MetricAgeOffIterator.java

private void seekIfNecessary() {
    while (super.hasTop()) {
        // ... skipping logic with continue ...
        return; // Exit when valid data found or source exhausted
    }
}

2. Stabilized TimeSeriesGroupingIteratorTest (Flaky TimeSeriesGroupingIteratorTest #242)

The test suite relied on System.currentTimeMillis() for data generation, which resulted in non-deterministic failures depending on execution timing.

This was fixed by replacing dynamic timestamps with a fixed base timestamp to ensure reproducibility.

TimeSeriesGroupingIteratorTest.java

- long ts = ((System.currentTimeMillis() / 1000) * 1000);
+ long ts = 1705400000000L; // Fixed timestamp for reproducibility

3. Cleanup of FastClasspathScanner (FastClasspathScanner is outdated -- consider porting to ClassGraph #169)

The project has fully transitioned to ClassGraph.
As a result, the unused version.fast-classpath-scanner property was removed from the root pom.xml.

pom.xml

- <version.fast-classpath-scanner>3.1.13</version.fast-classpath-scanner>

Verification Results :

Code Review :

Verified that the StackOverflowError fix eliminates all recursive calls from the skipping logic.

Confirmed that test stabilization uses fixed timestamps across all relevant test methods.