WebGPU: Fix glow layer when using opacity

[Popov72]

See https://forum.babylonjs.com/t/error-with-babylon-7-0-and-webgpu-using-glowlayer-and-advanceddynamictexture/54982

[bjsplat]

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[bjsplat]

Snapshot stored with reference name:
refs/pull/15883/merge

Test environment:
https://snapshots-cvgtc2eugrd3cgfd.z01.azurefd.net/refs/pull/15883/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:

https://playground.babylonjs.com/?snapshot=refs/pull/15883/merge
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[bjsplat]

Visualization tests for WebGPU (Experimental)

https://snapshots-cvgtc2eugrd3cgfd.z01.azurefd.net/refs/pull/15883/merge/testResults/webgpuplaywright/index.html

[bjsplat]

WebGL2 visualization test reporter:

https://snapshots-cvgtc2eugrd3cgfd.z01.azurefd.net/refs/pull/15883/merge/testResults/webgl2playwright/index.html