feat(system-metrics): cpu usage

[mario-launchdarkly]

• add scheduler for gather system metrics
• add cpu usage metrics

---

Note

Introduce a new system metrics module to periodically record CPU utilization and wire it into Observability; update instrumentation/exporters and headers accordingly.

• System Metrics (new modules):
  • Add System and SystemLive targets with CPU monitoring: CPUStatistics, SystemInfo, CPULoad, Scheduler, and live facade to periodically record system.cpu.utilization with cpu.logical_number and cpu.mode attributes.
• Observability integration:
  • ObservabilityClient builds SystemInfo and starts monitoring on init; falls back to SystemInfo.noOp on failure.
  • Extend semantic conventions with LDSemanticAttribute.System keys.
• Instrumentation/OTel updates:
  • Make Instrumentation.noOp a static value; use non-optional otelTracer and simplify span building.
  • Switch OTLP exporters to .init(config: .init(headers: ...)); update Meter provider views and merge resource attributes into gauge metrics.
• Plugin/headers:
  • Ensure highlight.project_id is present in customHeaders during registration; enrich resource attributes with SDK version/project id.
• Package/ExampleApp:
  • Wire new targets (System, SystemLive) into Observability target and Package.swift.
  • Set serviceName in Example app options.

^{Written by Cursor Bugbot for commit bf4fcb4. This will update automatically on new commits. Configure here.}