[MLIR][affine-loop-fusion] Handle defining ops between the source and dest loops

This patch handles defining ops between the source and dest loop nests, and prevents loop nests with `iter_args` from being fused.

If there is any SSA value in the dest loop nest whose defining op has dependence from the source loop nest, we cannot fuse the loop nests.

If there is a `affine.for` with `iter_args`, prevent it from being fused.

Reviewed By: dcaballe, bondhugula

Differential Revision: https://reviews.llvm.org/D97030