Make operator<<() wrap long EValue lists (#480)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/480

Wrap long lists at ten items per line. I considered adding another stream manipulator to let users modify this, but it seemed less immediately useful than the "edge_items" manipulator.

Also considered wrapping at a particular column number, but it's way easier to count items then to count characters.

The indenting on some of the nested elements like Tensors and Tensor lists aren't the best, but we can fix that in a future diff.
ghstack-source-id: 201868941
exported-using-ghexport

Reviewed By: JacobSzwejbka

Differential Revision: D49607605

fbshipit-source-id: 499472554ec899ea2bb51da26bae6b3559bab6fb