New Issue: Improve sparse matrix printing format

27181, "bradcray", "Improve sparse matrix printing format", "2025-04-29T21:15:22Z"

Today, Chapel's sparse arrays, like its dense ones, print the array values without any formatting or indication of the indices. As a result, a sparse tridiagonal matrix whose values are all 2.0 might look like:

2.0 2.0
2.0 2.0 2.0
2.0 2.0 2.0
2.0 2.0 2.0
2.0 2.0 2.0
2.0 2.0 2.0
2.0 2.0 2.0
2.0 2.0 2.0
2.0 2.0 2.0
2.0 2.0

This issue asks how we should output sparse arrays. We should also think about what it means to read in a sparse matrix.