Add propertiesSupplier support to EmfMetricLoggingPublisher

[humanzz]

Closes #6595

Enable EmfMetricLoggingPublisher to accept an optional Supplier<Map<String, String>> for enriching EMF records with custom properties at publish time.

Motivation and Context

Users of EmfMetricLoggingPublisher have no way to add custom metadata (e.g. Lambda request IDs, trace IDs) to EMF records. The aws-embedded-metrics-java library supports this via putProperty(), but the SDK's built-in publisher does not. This change adds a propertiesSupplier to the builder, evaluated on each publish() call, allowing dynamic enrichment of EMF output with searchable properties in CloudWatch Logs Insights.

Modifications

• Add propertiesSupplier field and builder method to EmfMetricLoggingPublisher.Builder
• Add propertiesSupplier field, accessor, and builder setter to EmfMetricConfiguration, defaulting to empty map when null
• Add resolveProperties() to MetricEmfConverter which invokes the supplier from config once per convert call, handling null returns and exceptions gracefully
• Add writeCustomProperties() to MetricEmfConverter which writes properties first in the EMF JSON so _aws, dimensions, and metrics overwrite any key collisions

Testing

Added 7 tests to MetricEmfConverterTest:

• Custom properties appear in EMF output
• No supplier configured produces identical output to current behavior
• Empty properties map produces no extra keys
• Property key matching _aws is overwritten by the real _aws object
• Property key matching a dimension name is overwritten by the real dimension value
• Property key matching a metric name is overwritten by the real metric value
• Batched EMF records (220 metrics, 3 batches) all contain custom properties

Added 3 tests to EmfMetricLoggingPublisherTest:

• Supplier throwing exception logs warning and publishes without custom properties
• Supplier returning null publishes without custom properties
• Stateful supplier returns different maps on successive publish calls

All 26 tests pass. mvn clean install -pl :emf-metric-logging-publisher succeeds (compile, checkstyle, tests, javadoc, API compatibility).

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
• I have added a changelog entry. Adding a new entry must be accomplished by running the scripts/new-change script and following the instructions. Commit the new file created by the script in .changes/next-release with your changes.
• 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