Disable replication recovery invariant that stableTimestamp equals appliedThrough

To support downgrade from 4.6 to 4.4 after removal of the stable optime candidates list, which will allow the stable timestamp to be set at a timestamp in the middle of a secondary batch, we should disable this invariant in replication recovery in 4.4. To see if the invariant catches any remaining storage engine bugs in our test infrastructure, we can allow the invariant to be enabled via a failpoint that we will enable in testing.