Sporadic test failure for a particular test seed.

**Build scan:**
https://gradle-enterprise.elastic.co/s/jbjwp6od7c6ji/tests/:libs:elasticsearch-tdigest:test/org.elasticsearch.tdigest.MergingDigestTests/testFewValues

**Reproduction line:**
```
./gradlew ':libs:elasticsearch-tdigest:test' --tests "org.elasticsearch.tdigest.MergingDigestTests.testFewValues" -Dtests.seed=6554AFFC73846D79 -Dtests.locale=es-BO -Dtests.timezone=Africa/Maputo -Druntime.java=20
```

**Applicable branches:**
8.9

**Reproduces locally?:**
Yes

**Failure history:**
https://gradle-enterprise.elastic.co/scans/tests?tests.container=org.elasticsearch.tdigest.MergingDigestTests&tests.test=testFewValues

**Failure excerpt:**
```
java.lang.AssertionError: 0.6925480622462196 expected:<10.481852045585184> but was:<22.37554534626972>

  at __randomizedtesting.SeedInfo.seed([6554AFFC73846D79:47F980E061350D82]:0)
  at org.junit.Assert.fail(Assert.java:88)
  at org.junit.Assert.failNotEquals(Assert.java:834)
  at org.junit.Assert.assertEquals(Assert.java:553)
  at org.elasticsearch.tdigest.TDigestTests.testFewValues(TDigestTests.java:343)
  at jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
  at java.lang.reflect.Method.invoke(Method.java:578)
  at com.carrotsearch.randomizedtesting.RandomizedRunner.invoke(RandomizedRunner.java:1758)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$8.evaluate(RandomizedRunner.java:946)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$9.evaluate(RandomizedRunner.java:982)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$10.evaluate(RandomizedRunner.java:996)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.tests.util.TestRuleSetupTeardownChained$1.evaluate(TestRuleSetupTeardownChained.java:48)
  at org.apache.lucene.tests.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at org.apache.lucene.tests.util.TestRuleThreadAndTestName$1.evaluate(TestRuleThreadAndTestName.java:45)
  at org.apache.lucene.tests.util.TestRuleIgnoreAfterMaxFailures$1.evaluate(TestRuleIgnoreAfterMaxFailures.java:60)
  at org.apache.lucene.tests.util.TestRuleMarkFailure$1.evaluate(TestRuleMarkFailure.java:44)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$StatementRunner.run(ThreadLeakControl.java:390)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl.forkTimeoutingTask(ThreadLeakControl.java:843)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$3.evaluate(ThreadLeakControl.java:490)
  at com.carrotsearch.randomizedtesting.RandomizedRunner.runSingleTest(RandomizedRunner.java:955)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$5.evaluate(RandomizedRunner.java:840)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$6.evaluate(RandomizedRunner.java:891)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$7.evaluate(RandomizedRunner.java:902)
  at org.apache.lucene.tests.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.tests.util.TestRuleStoreClassName$1.evaluate(TestRuleStoreClassName.java:38)
  at com.carrotsearch.randomizedtesting.rules.NoShadowingOrOverridesOnMethodsRule$1.evaluate(NoShadowingOrOverridesOnMethodsRule.java:40)
  at com.carrotsearch.randomizedtesting.rules.NoShadowingOrOverridesOnMethodsRule$1.evaluate(NoShadowingOrOverridesOnMethodsRule.java:40)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at org.apache.lucene.tests.util.TestRuleAssertionsRequired$1.evaluate(TestRuleAssertionsRequired.java:53)
  at org.apache.lucene.tests.util.AbstractBeforeAfterRule$1.evaluate(AbstractBeforeAfterRule.java:43)
  at org.apache.lucene.tests.util.TestRuleMarkFailure$1.evaluate(TestRuleMarkFailure.java:44)
  at org.apache.lucene.tests.util.TestRuleIgnoreAfterMaxFailures$1.evaluate(TestRuleIgnoreAfterMaxFailures.java:60)
  at org.apache.lucene.tests.util.TestRuleIgnoreTestSuites$1.evaluate(TestRuleIgnoreTestSuites.java:47)
  at com.carrotsearch.randomizedtesting.rules.StatementAdapter.evaluate(StatementAdapter.java:36)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl$StatementRunner.run(ThreadLeakControl.java:390)
  at com.carrotsearch.randomizedtesting.ThreadLeakControl.lambda$forkTimeoutingTask$0(ThreadLeakControl.java:850)
  at java.lang.Thread.run(Thread.java:1623)

```
libs/tdigest/src/test/java/org/elasticsearch/tdigest/TDigestTests.java
TDigest hist1 = factory().create();
        List<Double> data = new ArrayList<>();
        for (int j = 0; j < 100; j++) {
            for (double x : samples) {
                data.add(x);
                hist1.add(x);
            }
        }
        TDigest hist2 = factory().create();
        hist1.compress();
        hist2.add(hist1);
        Collections.sort(data);
        hist2.compress();
        double x1 = hist1.quantile(0.5);
        double x2 = hist2.quantile(0.5);
        assertEquals(Dist.quantile(0.5, data), x1, 0.2);
        assertEquals(x1, x2, 0.01);
    }
    /**
     * Brute force test that cdf and quantile give reference behavior in digest made up of all singletons.
     */
    public void testSingletonQuantiles() {
        double[] data = new double[11];
        TDigest digest = factory().create();
        for (int i = 0; i < data.length; i++) {
            digest.add(i);
            data[i] = i;
        }
        for (double x = digest.getMin() - 0.1; x <= digest.getMax() + 0.1; x += 1e-3) {
            assertEquals(String.valueOf(x), Dist.cdf(x, data), digest.cdf(x), 0.1);