[CI] EsqlClientYamlIT test {p0=esql/70_locale/Date format with Italian locale} failing

[elasticsearchmachine]

Build Scans:

• elasticsearch-intake #10160 / 8.16.0_bwc-snapshots
• elasticsearch-pull-request #32906 / 8.16.0_bwc-snapshots
• elasticsearch-pull-request #32889 / 8.16.0_bwc-snapshots
• elasticsearch-intake #10157 / 8.16.0_bwc-snapshots
• elasticsearch-pull-request #32887 / 8.16.0_bwc-snapshots
• elasticsearch-pull-request #32051 / 8.16.0_bwc-snapshots
• elasticsearch-intake #9878 / 8.16.0_bwc-snapshots
• elasticsearch-pull-request #31964 / 8.16.0_bwc-snapshots

Reproduction Line:

./gradlew ":x-pack:plugin:esql:qa:server:mixed-cluster:v8.16.0#yamlRestTest" -Dtests.class="org.elasticsearch.xpack.esql.qa.mixed.EsqlClientYamlIT" -Dtests.method="test {p0=esql/70_locale/Date format with default locale}" -Dtests.seed=4FCEC800A0DA3B0C -Dtests.bwc=true -Dtests.locale=ga -Dtests.timezone=Africa/Mbabane -Druntime.java=22

Applicable branches:
main

Reproduces locally?:
N/A

Failure History:
See dashboard

Failure Message:

java.lang.AssertionError: Failure at [esql/70_locale:29]: got unexpected warning header [
	299 Elasticsearch-8.16.0-f7911fedf5e5c6e5d645c45805d0d18d1dae53c8 "Date format [MMMM] contains textual field specifiers that could change in JDK 23. For more information, see https://ela.st/jdk-23-locales"
]

Issue Reasons:

• [main] 2 consecutive failures in test test {p0=esql/70_locale/Date format with Italian locale}
• [main] 3 consecutive failures in step 8.16.0_bwc-snapshots
• [main] 8 failures in test test {p0=esql/70_locale/Date format with Italian locale} (0.9% fail rate in 935 executions)
• [main] 8 failures in step 8.16.0_bwc-snapshots (2.2% fail rate in 368 executions)
• [main] 3 failures in pipeline elasticsearch-intake (2.3% fail rate in 132 executions)
• [main] 5 failures in pipeline elasticsearch-pull-request (1.4% fail rate in 347 executions)

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

[elasticsearchmachine]

This has been muted on branch main

Mute Reasons:

• [main] 5 failures in test test {p0=esql/70_locale/Date format with Italian locale} (0.5% fail rate in 929 executions)
• [main] 5 failures in step 8.16.0_bwc-snapshots (1.4% fail rate in 364 executions)
• [main] 2 failures in pipeline elasticsearch-intake (1.5% fail rate in 131 executions)
• [main] 3 failures in pipeline elasticsearch-pull-request (0.9% fail rate in 346 executions)

Build Scans:

• elasticsearch-intake #10157 / 8.16.0_bwc-snapshots
• elasticsearch-pull-request #32887 / 8.16.0_bwc-snapshots
• elasticsearch-pull-request #32051 / 8.16.0_bwc-snapshots
• elasticsearch-intake #9878 / 8.16.0_bwc-snapshots
• elasticsearch-pull-request #31964 / 8.16.0_bwc-snapshots

[elasticsearchmachine]

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

[luigidellaquila]

@thecoop what's the Java 23 alternative for "MMMM" date pattern?
If any... I see we are checking the pattern [BEGOavz]|LLL|MMM|QQQ|qqq|ccc|eee|(?<!Z)Z{4}(?!Z) to identify the potentially incompatible ones, so maybe it's just a clash with "MMM"?

[thecoop]

MMM deliberately also matches MMMM - its a textual date format that could change with JDK 23. It just needs to be added as an allowed warning on 8.x and 8.15, in a similar style to #113474