WebGPU: Improve copy video to texture

[Popov72]

Fix #13238

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Snapshot stored with reference name:
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Test environment:
https://babylonsnapshots.z22.web.core.windows.net/refs/pull/13254/merge/index.html

To test a playground add it to the URL, for example:

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Links to test babylon tools with this snapshot:

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https://sandbox.babylonjs.com/?snapshot=refs/pull/13254/merge
https://gui.babylonjs.com/?snapshot=refs/pull/13254/merge
https://nme.babylonjs.com/?snapshot=refs/pull/13254/merge

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