[mlir][sparse] Introduce new binary and unary op

When the sparse_tensor dialect lowers linalg.generic,
it makes inferences about how the operations should
affect the looping logic. For example, multiplication
is an intersection while addition is a union of two
sparse tensors.

The new binary and unary op separate the looping logic
from the computation by nesting the computation code
inside a block which is merged at the appropriate level
in the lowered looping code.

The binary op can have custom computation code for the
overlap, left, and right sparse overlap regions. The
unary op can have custom computation code for the
present and absent values.

Reviewed by: aartbik

Differential Revision: https://reviews.llvm.org/D121018