The WTPrepareConflictForReads is checked within wiredTigerPrepareConflictRetry which is an especially hot path. Some storage intensive queries spend more than one percent of their time just checking this fail point.

Furthermore, the fail point is only used in one test which the storage exec team has agreed is of little value, and can be replaced with a unit test.

This task is to:
a) Remove WTPrepareConflictForReads and associated test.
b) Add a unit test for wiredTigerPrepareConflictRetry which provides a special callback that will simulate prepare conflicts.