Simplification may need to preserve record length

[Philip Stoev]

For a certain small class of optimizer bugs, simplification that removes all unnecessary columns produces an non-repeatable test case. The reason is that the total record length decreases, making full table scans more likely.

Therefore, simplification should try to either remove all columns, or replace them with a single CHAR() column whose length is equal to the sum of the length of the removed columns.