Add missing constants, stub functions, and Node.js-specific extensions
to improve compatibility with code that expects Node.js perf_hooks APIs:

- Add 13 missing constants (entry types and milestones)
- Add standalone eventLoopUtilization() and timerify() function exports
- Add nodeTiming property to the performance object (via Proxy)
- Change eventLoopUtilization() to return stub values instead of throwing
- Change markResourceTiming() to no-op instead of throwing

These changes follow the stub approach (returning default values) rather
than throwing errors, which improves compatibility with libraries that
check for API existence but may not need the actual functionality.

Per review feedback, moved nodeTiming from TypeScript Proxy wrapper to the
C++ Performance class. This makes nodeTiming available on globalThis.performance
when the enable_nodejs_perf_hooks_module flag is enabled.

Changes:
- Added PerformanceNodeTiming class extending PerformanceEntry in C++
- Added nodeTiming property to Performance class (conditional on flag)
- Removed Proxy wrapper from TypeScript, now simple re-export
- Updated type snapshots with new PerformanceNodeTiming interface

Address PR review feedback:
- Change PerformanceNodeTiming properties from prototype to instance
  properties to match Node.js behavior where Reflect.ownKeys() includes
  all properties as own properties
- Add missing uvMetricsInfo property that returns libuv event loop
  metrics (stub values since actual metrics aren't available in workerd)
- Update toJSON() to include uvMetricsInfo in the output
- Regenerate TypeScript definitions

JSG_STRUCT value types don't need memory tracking as they are passed
by value to/from JavaScript and don't persist as embedder objects.