This PR makes the following improvements to `vector.scatter` and its
lowering pipeline:
- In addition to `memref`, accept a ranked `tensor` as the base operand
of `vector.scatter`, similar to `vector.transfer_write`.
- Implement bufferization support for `vector.scatter`, so that
tensor-based scatter ops can be fully lowered to memref-based forms.

It's worth to complete the functionality of map_scatter decomposition.
Full discussion can be found here:
https://github.com/iree-org/iree/issues/21135

---------

Signed-off-by: Ryutaro Okada <1015ryu88@gmail.com>

Add a new unit attribute to allow for unsigned integer comparison.

Example:
```mlir
scf.for unsigned %iv_32 = %lb_32 to %ub_32 step %step_32 : i32 {
  // body
}
```

Discussion:
https://discourse.llvm.org/t/scf-should-scf-for-support-unsigned-comparison/84655

See https://github.com/llvm/llvm-project/pull/147168 for more info.

This PR is part of the last step to remove `vector.extractelement` and `vector.insertelement` ops.
RFC: https://discourse.llvm.org/t/rfc-psa-remove-vector-extractelement-and-vector-insertelement-ops-in-favor-of-vector-extract-and-vector-insert-ops

It updates the Sparse Vectorizer to use `vector.extract` and `vector.insert` instead of `vector.extractelement` and `vector.insertelement`.

The revision adds isOneInteger helper, and simplifies the existing code
with the two methods. It removes some lambda, which makes code cleaner.

For downstream users, you can update the code with the below script.

```bash
sed -i "s/isZeroIndex/isZeroInteger/g" **/*.h
sed -i "s/isZeroIndex/isZeroInteger/g" **/*.cpp
```

---------

Signed-off-by: hanhanW <hanhan0912@gmail.com>

Currently, the lowering for vector.step lives
under a folder. This is not ideal if we want
to do transformation on it and defer the
 materizaliztion of the constants much later.

This commits adds a rewrite pattern that
could be used by using
`transform.structured.vectorize_children_and_apply_patterns`
transform dialect operation.

Moreover, the rewriter of vector.step is also
now used in -convert-vector-to-llvm pass where
it handles scalable and non-scalable types as
LLVM expects it.

As a consequence of removing the vector.step
lowering as its folder, linalg vectorization
will keep vector.step intact.

Because the sparse vectorizer relies on the code coming out of the
sparsifier, the "patterns" are not always made very general. However, a
recent change in the generated code revealed an obvious situation where
the subscript analysis could be made a bit more robust.

Fixes:
https://github.com/llvm/llvm-project/issues/79897