[ET-VK] Changing texture access pattern for conv2d dw ops to improve performance.

This diff changes the texture access pattern for convolutional depthwise (DW) operations in Executorch's Vulkan backend to iterate first on x axis then y and then z to improve performance.

Differential Revision: [D67770160](https://our.internmc.facebook.com/intern/diff/D67770160/)

[ghstack-poisoned]

Author: trivedivivek

backends/vulkan/runtime/graph/ops/glsl/conv2d_dw.glsl

@@ -35,7 +35,10 @@ layout(local_size_x_id = 0, local_size_y_id = 1, local_size_z_id = 2) in;
  * output at a single output location.
  */
 void main() {
-  const ivec3 pos = ivec3(gl_GlobalInvocationID);
+  const ivec3 pos = ivec3(
+    gl_GlobalInvocationID.x % out_limits.x,
+    (gl_GlobalInvocationID.x / out_limits.x) % out_limits.y,
+    gl_GlobalInvocationID.x / (out_limits.x * out_limits.y));
 
   if (any(greaterThanEqual(pos, out_limits))) {
     return;

backends/vulkan/runtime/graph/ops/glsl/conv2d_dw_output_tile.glsl

@@ -39,7 +39,10 @@ layout(local_size_x_id = 0, local_size_y_id = 1, local_size_z_id = 2) in;
  * output at a single output location.
  */
 void main() {
-  const u16vec3 pos = u16vec3(gl_GlobalInvocationID);
+  const u16vec3 pos = u16vec3(
+    gl_GlobalInvocationID.x % out_limits.x,
+    (gl_GlobalInvocationID.x / out_limits.x) % out_limits.y,
+    gl_GlobalInvocationID.x / (out_limits.x * out_limits.y));
 
   if (any(greaterThanEqual(pos, out_limits))) {
     return;

backends/vulkan/runtime/graph/ops/impl/Convolution.cpp

@@ -372,7 +372,7 @@ void add_conv2d_node(
 
   utils::uvec3 wg_size = create_conv2d_global_wg_size(graph, method, out);
 
-  if (method == Conv2dMethod::Pointwise) {
+  if (method == Conv2dMethod::Pointwise || method == Conv2dMethod::Depthwise) {
     wg_size = {wg_size[0] * wg_size[1] * wg_size[2], 1, 1};
   }