Right now the default for such case is DenseIntElementAttr, however because it
is so generic its API is quite hard to use and it is easy to either materialize
individual elements as individual IntegerAttr or as APInt. It is also not
possible to easily get an ArrayRef<int64>.
D116394 is an illustration of the effect of this new attribute on a recent part of
the codebase (the TOSA dialect). There is saves multiple traversals of ArrayAttr
and local creation of SmallVector<int64_t> in various situation.