This came out of investigating the replica_sets failures after setting EMRC=true in EFT. See this patch.

In rollback_all_op_types.js and rollback_ddl_op_sequences.js, we are using rollbackViaRefetch despite EMRC=true. This is because EFT does not support recoverToStableTimestamp. We need to add this support before making EMRC=true the default.