Release command buffer references after submit

[jakubmaniak]

Releases GPUCommandBuffer references after queue.submit(...).

This fixes a memory leak caused by the fact that <GPUCommandBuffer>._destroy() is only available internally
and cannot be called by users directly (without as any hack).
The leak becomes noticeable when command buffers are continuously created and submitted in a render loop.

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GPUCommandBuffer objects are one-time-use according to the WebGPU specification - they do not need to be kept alive after submission.

Note: Once a GPUCommandBuffer object has been submitted, it cannot be used again.

Source: https://developer.mozilla.org/en-US/docs/Web/API/GPUCommandBuffer

Tested on:

• Windows 10 (x86_64)
• Windows 11 (x86_64)
• Linux Mint 22.3 (x86_64)

macOS not tested yet.