* Refactor MonitoredItem.ValueChanged & cert validation
Refactored MonitoredItem.ValueChanged for correctness, performance, and comprehensive test coverage, including improved deadband and array handling. Rewrote equality logic for Variants and arrays. Made certificate validation thread-safe using ConcurrentDictionary and proper semaphore usage. Added extensive unit tests and benchmarks for value change detection.
* Implement DiagnosticsNodeManager using AsyncCustomNodeManager
* Implement CoreNodeManager using AsyncCustomNodeManager