Use as_image_copy where possible (#10733)

# Objective

`wgpu` has a helper method `texture.as_image_copy()` for a common
pattern when making a default-like `ImageCopyTexture` from a texture.

This is used in various places in Bevy for texture copy operations, but
it was not used where `write_texture` is called.

## Solution

- Replace struct `ImageCopyTexture` initialization with
`texture.as_image_copy()` where appropriate

Signed-off-by: Torstein Grindvik <torstein.grindvik@muybridge.com>
Co-authored-by: Torstein Grindvik <torstein.grindvik@muybridge.com>

crates/bevy_pbr/src/render/mesh.rs

@@ -377,12 +377,7 @@ impl FromWorld for MeshPipeline {
 
             let format_size = image.texture_descriptor.format.pixel_size();
             render_queue.write_texture(
-                ImageCopyTexture {
-                    texture: &texture,
-                    mip_level: 0,
-                    origin: Origin3d::ZERO,
-                    aspect: TextureAspect::All,
-                },
+                texture.as_image_copy(),
                 &image.data,
                 ImageDataLayout {
                     offset: 0,

crates/bevy_sprite/src/mesh2d/mesh.rs

@@ -304,12 +304,7 @@ impl FromWorld for Mesh2dPipeline {
 
             let format_size = image.texture_descriptor.format.pixel_size();
             render_queue.write_texture(
-                ImageCopyTexture {
-                    texture: &texture,
-                    mip_level: 0,
-                    origin: Origin3d::ZERO,
-                    aspect: TextureAspect::All,
-                },
+                texture.as_image_copy(),
                 &image.data,
                 ImageDataLayout {
                     offset: 0,

crates/bevy_sprite/src/render/mod.rs

@@ -100,12 +100,7 @@ impl FromWorld for SpritePipeline {
 
             let format_size = image.texture_descriptor.format.pixel_size();
             render_queue.write_texture(
-                ImageCopyTexture {
-                    texture: &texture,
-                    mip_level: 0,
-                    origin: Origin3d::ZERO,
-                    aspect: TextureAspect::All,
-                },
+                texture.as_image_copy(),
                 &image.data,
                 ImageDataLayout {
                     offset: 0,