Change UNKNOWN_CODE_PLEASE_REPORT to identify uknown code

[glensc]

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

[dougwilson]

Please do not change the code property to be dymanic like this. The code property should work like it does in Node.js core as a single value without spaces. If you are trying to add the errno to the message, then just add it to the mesaage string.

[glensc]

@dougwilson 19aa86d