Update on "[ET-VK] Adding a common utility function to calculate 3d output position based on unique index."

This diff adds an indexing utils header file used in Vulkan backend of Executorch. The header file includes functions for converting a global index to u16 indices based on input sizes.

Differential Revision: [D67821941](https://our.internmc.facebook.com/intern/diff/D67821941/)

[ghstack-poisoned]

Author: trivedivivek

backends/vulkan/runtime/graph/ops/glsl/indexing_utils_u16.h

@@ -13,10 +13,7 @@
 
 u16vec3 idx_to_u16pos_x_wise(uint idx, int size_x, int size_y) {
   const uint div_by_x = idx / size_x;
-  return u16vec3(
-      idx % size_x,
-      div_by_x % size_y,
-      div_by_x / size_y);
+  return u16vec3(idx % size_x, div_by_x % size_y, div_by_x / size_y);
 }
 
 #endif // INDEXING_UTILS_U16_H