Implement the conversion from sparse constant to sparse tensors.

The sparse constant provides a constant tensor in coordinate format. We first split the sparse constant into a constant tensor for indices and a constant tensor for values. We then generate a loop to fill a sparse tensor in coordinate format using the tensors for the indices and the values. Finally, we convert the sparse tensor in coordinate format to the destination sparse tensor format.

Add tests.

Reviewed By: aartbik

Differential Revision: https://reviews.llvm.org/D110373