WT-4676 is adding the functionality to search and return a record in the lookaside file directly as compared to instantiating the page with the entire lookaside information. At the moment, if the function encounters a WT_MODIFY it will return a copy of the modify to the user, which is not the right thing to do.

When the search settles on a modify record, it needs to start building a list of modifies all the way upto the base update. Then mash these together into the final value and return it to the caller.

__wt_value_return_upd() does something similar, and potentially that code can be reused?

This ticket will also update the test from WT-4678 to confirm we are doing the right thing