Refactor event handler namings.

Source/MQTTnet.Extensions.ManagedClient/ManagedProcessFailedEventArgs.cs

@@ -0,0 +1,14 @@
+using System;
+
+namespace MQTTnet.Extensions.ManagedClient
+{
+    public class ManagedProcessFailedEventArgs : EventArgs
+    {
+        public ManagedProcessFailedEventArgs(Exception exception)
+        {
+            Exception = exception;
+        }
+
+        public Exception Exception { get; }
+    }
+}