[ibm-mq] Add expired message metric for IBM MQ queues

[breedx-splk]

Resolves #2788. Slopvomited with codex.

I don't love that the metric type is gauge, but it's consistent with ibm.mq.uncommitted.messages as mentioned in the original issue. We should also probably give some follow-up consideration to the metric names, since committed and uncommitted could (in concept) just be attributes/dimensions on some ibm.mq.messages counter...but let's leave data model redesign for a follow-up PR effort, as demand calls for it.

[Copilot]

Pull request overview

Adds a new IBM MQ queue metric to report expired message counts (issue #2788) and wires it through collection, configuration, tests, and documentation.

Changes:

• Collect MQIACF_EXPIRY_Q_COUNT from MQCMD_INQUIRE_Q_STATUS and publish it as ibm.mq.expired.messages.
• Add a new config toggle (isIbmMqExpiredMessagesEnabled) and enable the metric in sample/test configs.
• Update the metrics model + generated docs and extend the unit test expectations.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
ibm-mq-metrics/src/main/java/io/opentelemetry/ibm/mq/metricscollector/InquireQStatusCmdCollector.java	Requests the additional PCF attribute for expiry/expired message count.
ibm-mq-metrics/src/main/java/io/opentelemetry/ibm/mq/metricscollector/QueueCollectionBuddy.java	Registers a new gauge mapping from MQIACF_EXPIRY_Q_COUNT to the new metric.
ibm-mq-metrics/src/main/java/io/opentelemetry/ibm/mq/metrics/Metrics.java	Defines the new ibm.mq.expired.messages gauge instrument.
ibm-mq-metrics/src/main/java/io/opentelemetry/ibm/mq/metrics/MetricsConfig.java	Adds enable/disable config plumbing for the new metric.
ibm-mq-metrics/src/test/java/io/opentelemetry/ibm/mq/metricscollector/QueueCollectionBuddyTest.java	Extends PCF request/response fixtures and assertions to cover the new metric.
ibm-mq-metrics/model/metrics.yaml	Adds the metric to the semantic model (name/unit/attributes).
ibm-mq-metrics/docs/metrics.md	Documents the new metric (generated doc output updated).
ibm-mq-metrics/config.yml	Enables the new metric in the example config (also includes a whitespace/indent adjustment).
ibm-mq-metrics/src/test/resources/conf/config.yml	Enables the new metric for unit tests.
ibm-mq-metrics/src/integrationTest/resources/conf/test-config.yml	Enables the new metric in integration test config.
ibm-mq-metrics/src/integrationTest/resources/conf/test-queuemgr-config.yml	Enables the new metric in integration test queue-manager config.