[mlir][OpDSL] Add arithmetic function attributes.

The revision extends OpDSL with unary and binary function attributes. A function attribute, makes the operations used in the body of a structured operation configurable. For example, a pooling operation may take an aggregation function attribute that specifies if the op shall implement a min or a max pooling. The goal of this revision is to define less and more flexible operations.

We may thus for example define an element wise op:
```
linalg.elem(lhs, rhs, outs=[out], op=BinaryFn.mul)
```
If the op argument is not set the default operation is used.

Depends On D120109

Reviewed By: nicolasvasilache, aartbik

Differential Revision: https://reviews.llvm.org/D120110