[CI] VerifierTests class failing

[elasticsearchmachine]

Build Scans:

• elasticsearch-periodic #4629 / release-tests
• elasticsearch-periodic #4624 / release-tests
• elasticsearch-periodic #4579 / release-tests
• elasticsearch-periodic #4574 / release-tests
• elasticsearch-periodic #4569 / release-tests
• elasticsearch-periodic #4564 / release-tests
• elasticsearch-periodic #4553 / release-tests
• elasticsearch-periodic #4548 / release-tests

Reproduction Line:

./gradlew ":x-pack:plugin:esql:test" --tests "org.elasticsearch.xpack.esql.analysis.VerifierTests.testQueryStringFunctionWithNonBooleanFunctions" -Dtests.seed=2AF28470B60B54A2 -Dbuild.snapshot=false -Dtests.jvm.argline="-Dbuild.snapshot=false" -Dlicense.key=x-pack/license-tools/src/test/resources/public.key -Dtests.locale=ar-TD -Dtests.timezone=Etc/GMT+12 -Druntime.java=23

Applicable branches:
8.16

Reproduces locally?:
N/A

Failure History:
See dashboard

Failure Message:

org.junit.ComparisonFailure: expected:<1:19: [Invalid condition [qstr("first_name: Anna") is not null]. Function QSTR can't be used with ISNOTNULL]> but was:<1:19: [Unknown function [qstr], did you mean [to_str]?]>

Issue Reasons:

• [8.16] 2 consecutive failures in step release-tests
• [8.16] 8 failures in class org.elasticsearch.xpack.esql.analysis.VerifierTests (1.5% fail rate in 551 executions)
• [8.16] 8 failures in step release-tests (88.9% fail rate in 9 executions)
• [8.16] 8 failures in pipeline elasticsearch-periodic (47.1% fail rate in 17 executions)

Note:
This issue was created using new test triage automation. Please report issues or feedback to es-delivery.

[elasticsearchmachine]

Pinging @elastic/es-analytical-engine (Team:Analytics)

[elasticsearchmachine]

Pinging @elastic/es-search-relevance (Team:Search Relevance)

[carlosdelest]

Addressing in #115791