[mlir][sparse] Add sparse_tensor.select operation

The new select operation allows filtering of sparse tensors
by conditionally keeping or removing each element. This
can be used to remove negative values or select the upper
triangle of a matrix.

The select op has a single region which operates on a single
value and must return a boolean True to keep or False to drop.

Reviewed by: aartbik

Differential Revision: https://reviews.llvm.org/D133569