Change UNKNOWN_CODE_PLEASE_REPORT to identify uknown code

Changes UNKNOWN_CODE_PLEASE_REPORT to include packet.errno in it.

This makes it easier to identify what the code is even if the code is not yet supported:

```
(node:1) UnhandledPromiseRejectionWarning: Error: UNKNOWN_CODE_PLEASE_REPORT: Query execution was interrupted, query_timeout exceeded
```

lib/protocol/sequences/Sequence.js

@@ -44,7 +44,7 @@ Sequence.prototype.hasErrorHandler = function() {
 
 Sequence.prototype._packetToError = function(packet) {
   var code = ErrorConstants[packet.errno] || 'UNKNOWN_CODE_PLEASE_REPORT';
-  var err  = new Error(code + ': ' + packet.message);
+  var err  = new Error(code + '[' + packet.errno + ']: ' + packet.message);
   err.code = code;
   err.errno = packet.errno;