[mlir][sparse] generalize sparse tensor output implementation

Moves sparse tensor output support forward by generalizing from injective
insertions only to include reductions. This revision accepts the case with all
parallel outer and all reduction inner loops, since that can be handled with
an injective insertion still. Next revision will allow the inner parallel loop
to move inward (but that will require "access pattern expansion" aka "workspace").

Reviewed By: bixia

Differential Revision: https://reviews.llvm.org/D114399