DX12: Align copies b/w textures and buffers when D3D12_FEATURE_DATA_D3D12_OPTIONS13.UnrestrictedBufferTextureCopyPitchSupported is false

[ErichDonGubler]

Connections

• Likely resolves [d3d12] Panic in end_encoding  #5285.
• A case we need to handle in order to fix [d3d12] Support padded rows_per_image for 3D texture writes #4150.

Testing

• TODO: Will prove that this works even when forced to align. This won't definitively prove that we're fixing cases that need this, but it will prove that we're not breaking anything with intermediate buffers.

Squash or Rebase?

rebase plz

Checklist

• If this contains user-facing changes, add a CHANGELOG.md entry.

[ErichDonGubler]

I'm...honestly not sure why this is failing on the wgpu_gpu::regression::issue_6827::test_scatter test entry in CI. I think I need some help. Marking as ready for review; perhaps @teoxoy or @cwfitzgerald could help me out?

[ErichDonGubler]

I'm thinking that the best time to clean these up might be during a Poll, where we can guarantee that temporary buffers are no longer necessary. Validation, please? 🥺

[teoxoy]

We can store them in the CommandEncoder and they will be cleaned up on CommandEncoder::Drop, wgpu-core holds HAL command encoders alive until the end of the submission.

[teoxoy]

The test is failing because of:

Panic: GraphicsCommandList::close failed: The parameter is incorrect. (0x80070057)

I'd run the test locally with the validation layers enabled to see if there is more info. I've seen the error come up in cases where we didn't uphold some D3D12 invariant while encoding.