This code in this branch assumes the `src` operand in
`insert_slice_async` always aliases the result, which shouldn't hold for
generally cases but is just a workaround to make the pipeline pass work.
I'm also working on the complete analysis in another
[branch](https://github.com/openai/triton-mlir/tree/keren/analyze-slice).
This PR does the following things:
- Code refactoring on Load and Store op codegen, rewrite with same logic
and share much code
- Support the vectorized load/store
