fix(worker): thread the completion cache through CreateForTesting

src/ZB.MOM.WW.MxGateway.Worker/MxAccess/MxAccessSession.cs

@@ -116,6 +116,9 @@ public sealed class MxAccessSession : IDisposable
             eventSink,
             handleRegistry ?? new MxAccessHandleRegistry(),
             valueCache ?? new MxAccessValueCache(),
+            eventSink is IWriteCompletionCacheProvider provider
+                ? provider.WriteCompletionCache
+                : new MxAccessWriteCompletionCache(),
             creationThreadId ?? Environment.CurrentManagedThreadId);
     }