In BF-30418 we discovered that dbCheck can hit a prepare conflict on secondaries and fail a wiredtirger invariant than a thread which encounters a prepare conflict must be killable.

We feel that dbCheck needs to enforce prepare conflicts for correctness, and the oplog applier thread should remain unkillable.

To fix this we should expand the PrepareConflictBehavior to be able to propagate an error instead of retrying the conflict (and running into the invariant mentioned). This will allow dbCheck to finish with a warning that a certain key range could not be validated