Runtime Metrics: Bun support

[chargome]

Bun inherits nodeRuntimeMetricsIntegration automatically but uses JavaScriptCore (not V8). Several APIs need special handling:

• perf_hooks.monitorEventLoopDelay() — throws NotImplementedError, must catch and skip
• v8.getHeapStatistics() — stub, needs bun:jsc.heapStats() fallback or skip
• performance.eventLoopUtilization() — partial, best-effort
• GC via PerformanceObserver — uncertain with JSC, needs validation

[linear-code]

JS-1956