Make roll a decomposition and remove its lowering (#119857)
We use the fact that we now propagate indexing properly to avoid having
to maintain two different implementations of the op. Doing this we also remove
a spurious guard on this op.
We move the ref into a decomp as we now use advanced indexing.
The only difference we did in the implementation is that we now use
advanced indexing rather than `torch.cat`.
We also remove it from core. Let's see how this goes.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/119857
Approved by: https://github.com/peterbell10, https://github.com/larryliu0820
ghstack dependencies: #119863, #119864
