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 non-default 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.