Move peephole optimization at the top of the flow pipeline (#7058)
Move peephole optimization at the top of the flow pipeline (#7058)

- Drop `-iree-flow-enable-1x1-conv-to-matmul` as it was true by default.
- Move the linalg -> linalg peephole optimizations passes to the top of the flow pipeline.
google/iree,iree-org/iree,google/iree,google/iree,google/iree,google/iree,iree-org/iree,iree-org/iree,iree-org/iree,iree-org/iree,iree-org/iree,google/iree,google/iree,iree-org/iree