Remove feature discovery query

[DarkWanderer]

It seems like in a lot of cases users prefer to create transient Connection instances. This leads to perceived slowdowns because of discovery query - #582 #626

Discovery query fetches server version and Time zone. Server version is used to discover server features which are only currently relevant for tests. Time zone is available in headers for every query

This will be a breaking API change and hence needs to happen in v8 major release