To ensure that all cursors/sessions are safe, we want the property that all created sessions from a wrapped connection are also wrapped. To achieve this, the internal WT_CONNECTION must be kept private and all uses of WT_CONNECTION should be migrated to WiredTigerConnection.

This is similar to how we enforce safe usage of wrapped sessions/cursors.

A few problems need to be solved to achieve this:
 - During shutdown the connection is closed and reopened several times, this behaviour needs to be somehow shared with the WiredTigerConnection.

 - event handlers depend on WT_CONNECTION* and we have no good way to map those to WiredTigerConnection

 - the KV engine is a heavy user of the raw WT_CONNECTION, we probably need to wrap its APIs the same way we do with WiredTigerSession and WiredTigerCursor