Correctly check cpu data size not just descriptor. (#22612)

# Objective

Fixes #22609.

## Solution

We need to also validate the cpu data size before we do any copies, etc.
We'll ignore the users descriptor size if the configured it wrong. Not
sure if we want to to warn or if there's any scenario where overwriting
the size wouldn't be the right call.

## Testing

`fps_overlay` no longer crashes.

Author: tychedelia

crates/bevy_render/src/storage.rs

@@ -164,8 +164,18 @@ impl RenderAsset for GpuShaderBuffer {
     ) -> Result<Self, PrepareAssetError<Self::SourceAsset>> {
         let had_data = source_asset.data.is_some();
 
+        // when cpu data is provided, the actual buffer size is determined by the vec length,
+        // not the descriptor size
+        let actual_size = source_asset
+            .data
+            .as_ref()
+            .map(|d| d.len() as u64)
+            .unwrap_or(source_asset.buffer_description.size);
+
         let buffer = if let Some(prev) = previous_asset
-            && prev.buffer_descriptor == source_asset.buffer_description
+            && prev.buffer_descriptor.size == actual_size
+            && prev.buffer_descriptor.usage == source_asset.buffer_description.usage
+            && prev.buffer_descriptor.label == source_asset.buffer_description.label
             && source_asset
                 .buffer_description
                 .usage
@@ -210,7 +220,10 @@ impl RenderAsset for GpuShaderBuffer {
 
         Ok(GpuShaderBuffer {
             buffer,
-            buffer_descriptor: source_asset.buffer_description,
+            buffer_descriptor: wgpu::BufferDescriptor {
+                size: actual_size,
+                ..source_asset.buffer_description
+            },
             had_data,
         })
     }