This MR adds the `lower-vector-multi-reduction` pass to lower the
vector.multi_reduction operation.
While the Transform Dialect includes an operation,
`transform.apply_patterns.vector.lower_multi_reduction`, intended for a
similar purpose, its utility is limited to projects that have adopted
the Transform Dialect. Recognizing that not all projects are equipped to
integrate this dialect, the proposed pass serves as a vital standalone
alternative. It ensures that projects solely dependent on the
traditional pass infrastructure can also benefit from the optimized
lowering of `multi_reduction` operation.
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Co-authored-by: Xiaolei Shi <xiaoleis@nvidia.com>