WT-10572 describes the difficulties in getting full column store testing in test format with predictable replay.  We do allow a reduced version of testing variable column store that disallows inserts with predictable replay.  This allows an initial bulk load of a file, and reads, updates, modifies, we just don't add new elements to the key space.  That at least gives us a bunch of column store testing without much complication.  That testing is done for variable len column store, but it isn't available for fixed len column store.  We should add the same level of testing for fixed len as we do for var len.