Preserve jvm.gc.name attribute in AppSignals GC runtime metrics - #2218

Summary

Preserves the name label (which carries the jvm.gc.name OTel attribute) on the aggregate JVMGCCount and JVMGCDuration AppSignals runtime metrics, enabling downstream consumers to differentiate GC collector types.

Problem

The JVMGCCount and JVMGCDuration transform rules in appsignals_runtime_config.yaml used label_set: [] in their aggregate_labels operation, which stripped all labels including the name attribute that identifies the GC collector type (e.g. PS Scavenge, G1 Young Generation).

Changes

• Changed label_set: [] to label_set: ["name"] for both JVMGCCount and JVMGCDuration transform rules
• Added unit test (TestAppSignalsGCMetricsPreserveNameLabel) that validates the name label is preserved

Testing

• Unit tests pass
• E2E: built A/B agent binaries (main vs. this branch) on EC2, ran both against a Java app using Parallel GC with ADOT instrumentation. Baseline EMF has no name field; this branch emits the name attribute on every GC record in CloudWatch Logs.

Example EMF record from the /aws/application-signals/data log group:

{
  "Environment": "eks:demo/default",
  "Service": "pet-clinic-frontend-java",
  "Telemetry.Source": "RuntimeMetric",
  "name": "PS Scavenge",
  "JVMGCCount": 7,
  "JVMGCDuration": 74,
  "_aws": {
    "CloudWatchMetrics": [{
      "Namespace": "ApplicationSignals",
      "Dimensions": [["Environment", "Service"]],
      "Metrics": [
        {"Name": "JVMGCCount", "Unit": "", "StorageResolution": 60},
        {"Name": "JVMGCDuration", "Unit": "", "StorageResolution": 60}
      ]
    }]
  }
}