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/conv2d_dw_output_tile.glsl

@@ -43,7 +43,7 @@ layout(local_size_x_id = 0, local_size_y_id = 1, local_size_z_id = 2) in;
 void main() {
   // y divided up by batch size is used to determine 3d position
   // since work size is calculated by x * ((y + B_Y - 1) / B_Y) * z
-  const uint out_limits_y_scaled = (out_limits.y + BATCH_SIZE_Y - 1) / BATCH_SIZE_Y;
+  const int out_limits_y_scaled = (out_limits.y + BATCH_SIZE_Y - 1) / BATCH_SIZE_Y;
 
   u16vec3 pos = idx_to_u16pos_x_wise(gl_GlobalInvocationID.x, out_limits.x, out_limits_y_scaled);