feat: port sessions 12 & 13 — Events/Monitoring/MsgTrace + Config Reload

Session 12 (218 features, IDs 854-950, 2166-2251, 2405-2439):
- EventTypes: system subjects, event message types, InternalState, ConnectEventMsg,
  DisconnectEventMsg, AccountNumConns, ServerIdentity, DataStats
- MonitorTypes: Connz, ConnInfo, ConnzOptions, ConnState, ProxyInfo, TlsPeerCert
- MonitorSortOptions: SortOpt, ConnInfos, all 13 sort comparers
- MsgTraceTypes: IMsgTrace, MsgTraceBase + 6 concrete types, custom JSON converter

Session 13 (89 features, IDs 2800-2888):
- ReloadOptions: IReloadOption interface, NoopReloadOption base, 50 option classes
  covering logging, TLS, auth, cluster, JetStream, MQTT, OCSP, misc

dotnet/src/ZB.MOM.NatsNet.Server/NatsServer.cs

@@ -57,7 +57,7 @@ public sealed partial class NatsServer : INatsServer
 
     private readonly ServerStats          _stats        = new();
     private readonly SlowConsumerStats    _scStats      = new();
-    private readonly StaleConnectionStats _staleStats   = new();
+    private readonly InternalStaleStats   _staleStats   = new();
 
     // =========================================================================
     // Core identity