ENH provide a short-circuit for CSR/CSC/BSR sum_duplicates
FIX implementation of has_canonical_format (was is_canonical)
Merge pull request #3271 from jnothman/has_canonical_format

ENH: sparse: provide a short-circuit for CSR/CSC/BSR sum_duplicates

Parallel to has_sorted_indices, this provides is_canonical, allowing sum_duplicates to be avoided in repeated operations.