[mlir][sparse] integrate sparse annotation into generic linalg op

This CL integrates the new sparse annotations (hereto merely added as fully
transparent attributes) more tightly to the generic linalg op in order to add
verification of the annotations' consistency as well as to make make other
passes more aware of their presence (in the long run, rewriting rules must
preserve the integrity of the annotations).

Reviewed By: nicolasvasilache

Differential Revision: https://reviews.llvm.org/D91224