LibIPC: Log actual decode errors when message parsing fails

Previously, when an IPC message failed to parse, we only logged
"Failed to parse IPC message" followed by a hex dump, making it
difficult to diagnose the actual cause.

Now we log the specific error from each endpoint's decode attempt,
making it much easier to identify issues like size limit violations
or invalid field values.

Libraries/LibIPC/Connection.h

@@ -102,6 +102,10 @@ protected:
         if (!peer_message.is_error())
             return peer_message.release_value();
 
+        dbgln("Failed to parse IPC message:");
+        dbgln("  Local endpoint error: {}", local_message.error());
+        dbgln("  Peer endpoint error: {}", peer_message.error());
+
         return nullptr;
     }
 };