Additional validation of buffer-texture copies (#7948)

* Additional validation of buffer-texture copies

Fixes #7936, but leaves a TODO for #7947

* Skip tests failing on dx12

* Update comments and change unwrap_or to expect

wgpu-types/src/lib.rs

@@ -2608,6 +2608,8 @@ impl TextureAspect {
     }
 }
 
+// There are some additional texture format helpers in `wgpu-core/src/conv.rs`,
+// that may need to be modified along with the ones here.
 impl TextureFormat {
     /// Returns the aspect-specific format of the original format
     ///