[PrimTorch] Add maker for *_copy variants of view functions (#87278)
Implements `diagonal_copy` as an example. This PR also fixes a number of
correcness issues with `diagonal_copy`.
cc @ezyang @mruberry @ngimel @Lezcano @fdrocha
Pull Request resolved: https://github.com/pytorch/pytorch/pull/87278
Approved by: https://github.com/mruberry
