Right now the bindings assume that all DenseElementsAttrs correspond to tensor values,
making it impossible to create vector-typed constants. I didn't want to change the API
significantly, so I opted for reusing the current signature of `.get`. Its `type` argument
now accepts both element types (in which case `shape` and `signless` can be specified too),
or a shaped type, which specifies the full type of the created attr (`shape` cannot be specified
in that case).
Reviewed By: ftynse
Differential Revision: https://reviews.llvm.org/D145053
99dee31ef4