The scope of this ticket is only to allow pre-fetching to be enabled in validation, but avoid actually turning it on. 

To do this, you would:

• Add a new function on the RecoveryUnit, (something named along the lines of 'setPrefetching' with a bool 'enable' as input.)
• Implement this function logic in WiredTigerRecoveryUnit to allow it to reconfigure the session to enable pre-fetch.
• Add a new function to enable pre-fetching to  ValidateState and ensure it gets called before initializeCollection()/initializeCursors().
• You will also need a destructor to disable pre-fetching in WiredTigerRecoveryUnit.

For the scope of this ticket, leave pre-fetching turned off. Turning on pre-fetching for validate will work done in a separate ticket.