[WebGPU] copy compressed textures fails when texture width is not div…

…isible by the block size

https://bugs.webkit.org/show_bug.cgi?id=264923
radar://118491364

Reviewed by Tadeu Zagallo.

To correctly write to compressed textures, the width of the data must be divisible
by the compressed texture's block size and we were not previously ensuring that.

Also clean up newBytesPerRow and levelInfoBytesPerRow duplication which were being
assigned the same value and never modified.

* LayoutTests/http/tests/webgpu/webgpu/api/operation/command_buffer/copyTextureToTexture-expected.txt:
Add test expectation as this passes locally.

* Source/WebGPU/WebGPU/Queue.mm:
(WebGPU::Queue::writeTexture):

Canonical link: https://commits.webkit.org/270881@main