Test failing with different args in the same run, all related to index out of bounds

**Build scan:**
https://gradle-enterprise.elastic.co/s/3bik4qiof2dei/tests/:x-pack:plugin:esql:test/org.elasticsearch.xpack.esql.expression.function.scalar.multivalue.MvConcatTests/testCrankyEvaluateBlockWithoutNulls%20%7BTestCase=KEYWORD%2F8%20KEYWORD%7D
**Reproduction line:**
```
./gradlew ':x-pack:plugin:esql:test' --tests "org.elasticsearch.xpack.esql.expression.function.scalar.multivalue.MvConcatTests.testCrankyEvaluateBlockWithoutNulls {TestCase=KEYWORD/8 KEYWORD}" -Dtests.seed=F0089FCA0A9B6D21 -Dbuild.snapshot=false -Dtests.jvm.argline="-Dbuild.snapshot=false" -Dtests.locale=sr-ME -Dtests.timezone=Africa/Mbabane -Druntime.java=21
```

**Applicable branches:**
8.11

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

**Failure history:**
https://gradle-enterprise.elastic.co/scans/tests?tests.container=org.elasticsearch.xpack.esql.expression.function.scalar.multivalue.MvConcatTests&tests.test=testCrankyEvaluateBlockWithoutNulls%20%7BTestCase%3DKEYWORD/8%20KEYWORD%7D


**Failure excerpt:**
```
java.lang.ArrayIndexOutOfBoundsException: Index 2 out of bounds for length 2

  at __randomizedtesting.SeedInfo.seed([F0089FCA0A9B6D21:9AE69939A4A7D1CF]:0)
  at org.elasticsearch.common.util.BigByteArray.get(BigByteArray.java:70)
  at org.elasticsearch.common.util.MockBigArrays$ByteArrayWrapper.get(MockBigArrays.java:388)
  at org.elasticsearch.common.util.BytesRefArray.get(BytesRefArray.java:109)
  at org.elasticsearch.compute.data.BytesRefArrayBlock.getBytesRef(BytesRefArrayBlock.java:50)
  at org.elasticsearch.xpack.esql.expression.function.scalar.multivalue.MvConcat$MvConcatEvaluator.eval(MvConcat.java:136)
  at org.elasticsearch.xpack.esql.expression.function.AbstractFunctionTestCase.testEvaluateBlock(AbstractFunctionTestCase.java:370)
  at org.elasticsearch.xpack.esql.expression.function.AbstractFunctionTestCase.testCrankyEvaluateBlockWithoutNulls(AbstractFunctionTestCase.java:283)
  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$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:1583)

```
server/src/main/java/org/elasticsearch/common/util/BigByteArray.java
++pageIndex;
                offset += copyLen;
                len -= copyLen;
                copyLen = Math.min(len, pageSize());
                System.arraycopy(buf, offset, pages[pageIndex], 0, copyLen);
            } while (len > copyLen);
        }
    }
    @Override
    public void fill(long fromIndex, long toIndex, byte value) {
        if (fromIndex > toIndex) {
            throw new IllegalArgumentException();
        }
        final int fromPage = pageIndex(fromIndex);
        final int toPage = pageIndex(toIndex - 1);
        if (fromPage == toPage) {
            Arrays.fill(pages[fromPage], indexInPage(fromIndex), indexInPage(toIndex - 1) + 1, value);
        } else {
            Arrays.fill(pages[fromPage], indexInPage(fromIndex), pages[fromPage].length, value);
            for (int i = fromPage + 1; i < toPage; ++i) {
                Arrays.fill(pages[i], value);
            }
            Arrays.fill(pages[toPage], 0, indexInPage(toIndex - 1) + 1, value);
        }
    }
    @Override
    public boolean hasArray() {
        return false;
    }
    @Override