[mlir][vector] Fix crash in ReorderCastOpsOnBroadcast with non-vector result (#170985)
Fixes a crash in `ReorderCastOpsOnBroadcast` by ensuring the cast result
is a `VectorType` before applying the pattern.
A regression test has been added to
mlir/test/Dialect/Vector/vector-sink.mlir.
Fixes: #126371