Looks like a leaked `Exchange`?

**Build scan:**
https://gradle-enterprise.elastic.co/s/mmrtyhckobkwo/tests/:x-pack:plugin:esql:internalClusterTest/org.elasticsearch.xpack.esql.action.EsqlActionIT/testShowFunctions

**Reproduction line:**
```
./gradlew ':x-pack:plugin:esql:internalClusterTest' --tests "org.elasticsearch.xpack.esql.action.EsqlActionIT.testShowFunctions" -Dtests.seed=8850B71504CB7FA5 -Dtests.locale=ar-EG -Dtests.timezone=Asia/Harbin -Druntime.java=21
```

**Applicable branches:**
main

**Reproduces locally?:**
Didn't try

**Failure history:**
https://gradle-enterprise.elastic.co/scans/tests?tests.container=org.elasticsearch.xpack.esql.action.EsqlActionIT&tests.test=testShowFunctions

**Failure excerpt:**
```
java.lang.AssertionError: Leftover exchanges ExchangeService{sinks=[xDupaxgARhq3e5LBrywuWw:4601], sources=[]} on node node_s0

  at org.junit.Assert.fail(Assert.java:88)
  at org.junit.Assert.assertTrue(Assert.java:41)
  at org.elasticsearch.xpack.esql.action.AbstractEsqlIntegTestCase.lambda$ensureExchangesAreReleased$0(AbstractEsqlIntegTestCase.java:38)
  at org.elasticsearch.test.ESTestCase.assertBusy(ESTestCase.java:1196)
  at org.elasticsearch.test.ESTestCase.assertBusy(ESTestCase.java:1169)
  at org.elasticsearch.xpack.esql.action.AbstractEsqlIntegTestCase.ensureExchangesAreReleased(AbstractEsqlIntegTestCase.java:38)
  at jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
  at java.lang.reflect.Method.invoke(Method.java:580)
  at com.carrotsearch.randomizedtesting.RandomizedRunner.invoke(RandomizedRunner.java:1758)
  at com.carrotsearch.randomizedtesting.RandomizedRunner$10.evaluate(RandomizedRunner.java:1004)
  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:1583)

```
x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/EsqlActionIT.java
assertThat(results.columns().stream().map(ColumnInfo::name).toList(), contains("b"));
        assertThat(results.columns().stream().map(ColumnInfo::type).toList(), contains("double"));
        assertThat(getValuesList(results), containsInAnyOrder(List.of(42d), List.of(44d)));
    }
    public void testFromProjectStatsGroupByAlias() {
        EsqlQueryResponse results = run("from test | rename data as d | keep d, count | stats avg(count) by d");
        logger.info(results);
        assertThat(results.columns().stream().map(ColumnInfo::name).toList(), contains("avg(count)", "d"));
        assertThat(results.columns().stream().map(ColumnInfo::type).toList(), contains("double", "long"));
        assertThat(getValuesList(results), containsInAnyOrder(List.of(42d, 1L), List.of(44d, 2L)));
    }
    public void testFromProjectStatsAggregateAlias() {
        EsqlQueryResponse results = run("from test | rename count as c | keep c, data | stats avg(c) by data");
        logger.info(results);
        assertThat(results.columns().stream().map(ColumnInfo::name).toList(), contains("avg(c)", "data"));
        assertThat(results.columns().stream().map(ColumnInfo::type).toList(), contains("double", "long"));
        assertThat(getValuesList(results), containsInAnyOrder(List.of(42d, 1L), List.of(44d, 2L)));
    }
    public void testFromEvalStats() {
        EsqlQueryResponse results = run("from test | eval ratio = data_d / count_d | stats avg(ratio)");
        logger.info(results);
        Assert.assertEquals(1, results.columns().size());
        Assert.assertEquals(1, getValuesList(results).size());
        assertEquals("avg(ratio)", results.columns().get(0).name());
        assertEquals("double", results.columns().get(0).type());
        assertEquals(1, getValuesList(results).get(0).size());
        assertEquals(0.034d, (double) getValuesList(results).get(0).get(0), 0.001d);
    }
    public void testUngroupedCountAll() {
        EsqlQueryResponse results = run("from test | stats count(*)");