Better generation of matrices to RREF by hand in LE2

[StevenClontz]

In https://github.com/TeamBasedInquiryLearning/linear-algebra/blob/main/exercises/outcomes/GT/GT2/generator.sage we wrote some logic to "undo" how a student might compute the determinant by hand, ensuring problems have similar difficulties.

I'd like to implement something similar for LE2: start with the "nice" RREF, then apply row operations to produce an interesting result that covers all the row op techniques we want to see from students.

[fragandi]

Upvote: some of my students did feel some versions of the problem were unfairly harder.