[telemetry] Consolidate service name metadata and complete resource field classifications

[hemarina]

Problem

The source telemetry registry declares the service.name runtime key twice: once through the OpenTelemetry semantic-convention key and once through a literal key. The declarations carry different metadata, so static GDPR reconciliation treats them as conflicting and cannot reliably classify the field.

The application-level service.name, service.version, and os.type declarations also need complete source classification and purpose metadata.

Expected behavior

• Each telemetry runtime key has one canonical exported AttributeKey declaration.
• Error telemetry reuses the canonical service-name key before the existing error. prefix is applied.
• Resource fields use the classifications and purposes already established by completed catalog entries:
  • service.name: System Metadata / Performance and Health
  • service.version: System Metadata / TI: Feature Usage
  • os.type: System Metadata / TI: Feature Usage
• Contributor review guidance catches duplicate keys and missing classification or purpose metadata.

Impact

The GDPR metadata exporter can produce complete, non-conflicting metadata for these resource fields without changing their emitted runtime key names.