Add tests to have one single form of `MatrixPrintForm` that is identical to the one generated by `basic_matrix_form`

[Melkiades]

A couple of differences:

• attributes(b$spans) # To do in original: remove dimnames
• b$row_info$node_class # to remove from original: attribute package rtables??
• compare_mf(a, b, TRUE) # indent in row_info should be different. Current fix
• b$formats[, 1] <- rep("", nrow(b$formats)) # To check original: We need to remove these spaces from formats?