Port reflection_pad1d to structured kernel (#55531)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/55531
Following https://github.com/pytorch/rfcs/blob/rfc-0005/RFC-0005-structured-kernel-definitions.md
Test Plan: unittests
Reviewed By: ezyang
Differential Revision: D27628059
fbshipit-source-id: 885a10b766db39f8f8df4dcaaf0769fcf2ff9751
