[mlir][vector] Fix crashes in `from_elements` folder + `broadcast` verifier (#155393)
This PR fixes two crashes / failures.
1. The `vector.broadcast` verifier did not take into account
`VectorElementTypeInterface` and was looking for int/index/float types.
2. The `vector.from_elements` folder attempted to create an invalid
`DenseElementsAttr`. Only int/float/index/complex types are supported.