[CI] MixedClusterEsqlSpecIT test {where-like.RlikeWithUpperTurnedInsensitive SYNC} failing

[elasticsearchmachine]

Build Scans:

• elasticsearch-periodic #8617 / 8.12.2_bwc
• elasticsearch-periodic #8611 / 8.11.4_bwc
• elasticsearch-periodic #8604 / 8.11.4_bwc
• elasticsearch-periodic #8592 / 8.11.4_bwc
• elasticsearch-periodic #8585 / 8.11.4_bwc

Reproduction Line:

./gradlew ":x-pack:plugin:esql:qa:server:mixed-cluster:v8.12.2#javaRestTest" -Dtests.class="org.elasticsearch.xpack.esql.qa.mixed.MixedClusterEsqlSpecIT" -Dtests.method="test {where-like.RlikeWithLowerConflictingFolded SYNC}" -Dtests.seed=2330B6AAC8F568C2 -Dtests.bwc=true -Dtests.locale=de-AT -Dtests.timezone=Europe/Gibraltar -Druntime.java=24

Applicable branches:
8.19

Reproduces locally?:
N/A

Failure History:
See dashboard

Failure Message:

org.elasticsearch.client.ResponseException: method [POST], host [http://[::1]:41641], URI [/_query?pretty=true&error_trace=true], status line [HTTP/1.1 400 Bad Request]
Warnings: [No limit defined, adding default limit of [500]]
¿eerror¿jroot_cause�¿dtypevverification_exceptionfreasonx�Found 1 problem
line 4:9: Unknown function [TO_UPPER], did you mean any of [to_ver, to_integer, to_ip, to_str, to_ulong, to_ul]?kstack_tracey
�org.elasticsearch.xpack.esql.analysis.VerificationException: Found 1 problem
line 4:9: Unknown function [TO_UPPER], did you mean any of [to_ver, to_integer, to_ip, to_str, to_ulong, to_ul]?
	at org.elasticsearch.xpack.esql.analysis.Analyzer.verify(Analyzer.java:120)
	at org.elasticsearch.xpack.esql.analysis.Analyzer.analyze(Analyzer.java:114)
	at org.elasticsearch.xpack.esql.session.EsqlSession.lambda$analyzedPlan$2(EsqlSession.java:145)
	at org.elasticsearch.xpack.esql.session.EsqlSession.lambda$preAnalyze$5(EsqlSession.java:170)
	at org.elasticsearch.server@8.12
[truncated]

Issue Reasons:

• [8.19] 5 failures in test test {where-like.RlikeWithUpperTurnedInsensitive SYNC} (2.5% fail rate in 198 executions)
• [8.19] 4 failures in step 8.11.4_bwc (66.7% fail rate in 6 executions)
• [8.19] 5 failures in pipeline elasticsearch-periodic (83.3% fail rate in 6 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)

[luigidellaquila]

This just needs to be excluded in v 8.11-12: TO_UPPER was added in v 8.13

[alex-spies]

@bpintea , there's a couple of these failures from tests that were added in #128393; would you mind taking a look?

[bpintea]

This just needs to be excluded in v 8.11-12: TO_UPPER was added in v 8.13

You're right, thanks @luigidellaquila.
(Would be great if we ran some bwc with maybe the earliest ESQL 8.x against 8.19 PRs, it'd have triggered this earlier.)