[jiterator] reduce kernel code duplication (#73908)
Summary:
Introduce `jiterator_code_stringify` to reduce duplication of kernel code used with jiterator.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/73908
Reviewed By: ngimel
Differential Revision: D34858716
Pulled By: mruberry
fbshipit-source-id: f87a34e4966b31620bbc5c7d93f0387fc1980ded
(cherry picked from commit 49fcc722a3d90b505400f7e2d98e199f7c0d71eb)
