TST tests for non-canonical input to sparse matrix operations

A number of sparse matrix formats are designed to treat duplicate values as their sum; they prefer indices in sorted order, but should be capable when unsorted. The current test suite largely compares functionality to numpy arrays/matrices, and so constructs sparse matrices from those, producing only _canonical_ sparse forms.

This introduces tests for non-canonical forms, but finds many test failures. I don't intend to fix them all here, but we can perhaps add known failure decorations.