[ET-VK] Simplifying conv1d op shader by changing it to process one output texel per thread. (#10690)

Pull Request resolved: #10665

This diff changes conv1d shader to process one output texel per thread, increasing GPU occupancy and improve performance.
ghstack-source-id: 282024192

Differential Revision: [D74097560](https://our.internmc.facebook.com/intern/diff/D74097560/)