Add WGPU_STRIDE_UNDEFINED and update bytesPerRow/rowsPerImage validation

This makes a nearly one-to-one mapping between the JS and C APIs, which
benefits projects like Blink and Emscripten.

- JavaScript's `undefined` is equivalent to C `WGPU_STRIDE_UNDEFINED`.
- JavaScript's `0` is equivalent to C `0`.
- To implement the API correctly, Blink must special-case an actual
  value coming in from JS that is equal to WGPU_STRIDE_UNDEFINED
  (0xFFFF'FFFF), and inject an error.

Keeps but deprecates a reasonable approximation of the old behavior.

Bug: dawn:520
Change-Id: Ie9c992ffab82830090d0dfc3120731e89cd9691c
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/31140
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>

src/tests/DawnTest.cpp

@@ -889,7 +889,7 @@ std::ostringstream& DawnTestBase::AddTextureExpectationImpl(const char* file,
     wgpu::TextureCopyView textureCopyView =
         utils::CreateTextureCopyView(texture, level, {x, y, slice}, aspect);
     wgpu::BufferCopyView bufferCopyView =
-        utils::CreateBufferCopyView(readback.buffer, readback.offset, bytesPerRow, 0);
+        utils::CreateBufferCopyView(readback.buffer, readback.offset, bytesPerRow, rowsPerImage);
     wgpu::Extent3D copySize = {width, height, 1};
 
     wgpu::CommandEncoder encoder = device.CreateCommandEncoder();