Update on "[ET-VK] Minor tuning for conv2d pw op to improve performance."

The diff introduces minor tuning for the Conv2d pointwise (PW) operation in the Vulkan backend to improve performance.
Conv 2d pw now issues a 2D dispatch instead of 1D, where dispatch axis y is now sized based on output texture's batch size.

Differential Revision: [D75251145](https://our.internmc.facebook.com/intern/diff/D75251145/)

[ghstack-poisoned]

Author: trivedivivek