[Dricmoy]

Motivation and Context

Closes #6840. LoggingMetricPublisher currently offers PLAIN and PRETTY, both of which can produce verbose logs when metrics are emitted frequently. A single-line format reduces repeated labels while keeping the collection hierarchy readable.

Modifications

• Add LoggingMetricPublisher.Format.COMPACT, producing output such as Metrics published: ApiCall{RetryCount=0,ApiCallAttempt{HttpStatusCode=200}}.
• Document the new public format and cover nested, sibling, and empty collections in unit tests.
• Add a release note generated with scripts/new-change.

Testing

Environment: macOS arm64, JDK 21, Maven wrapper 3.9.5. These commands targeted :metrics-spi and its required modules:

• ./mvnw -pl :metrics-spi -am test -Dspotbugs.skip=true -Dcheckstyle.skip=true — passed; 25 metrics-spi tests, including the new cases.
• ./mvnw -pl :metrics-spi -am validate -Dspotbugs.skip=true — passed with zero Checkstyle violations.
• ./mvnw -pl :metrics-spi -am package -Dskip.unit.tests=true -Dspotbugs.skip=true — passed; unit tests were run in the separate test command above.

SpotBugs was not verified locally: the initial run failed in the unchanged annotations module before reaching metrics-spi.

Screenshots (if appropriate)

N/A

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist

• I have read the CONTRIBUTING document
• Local run of mvn install succeeds
• My code follows the code style of this project
• My change requires a change to the Javadoc documentation
• I have updated the Javadoc documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed (focused reactor tests passed; full repository suite was not run)
• I have added a changelog entry using scripts/new-change
• My change is to implement 1.11 parity feature and I have updated LaunchChangelog

License

• I confirm that this pull request can be released under the Apache 2 license