Since #180397, all elements of a `DenseIntOrFPElementsAttr` are padded
to full bytes. This enables additional simplifications: whether a
`DenseIntOrFPElementsAttr` is a splat or not can now be inferred from
the size of the buffer. This was not possible before because a single
byte sometimes contained multiple `i1` elements.
Discussion:
https://discourse.llvm.org/t/denseelementsattr-i1-element-type/62525