Use texelFetch/textureLoad for WebGL2/WGSL

[sebavan]

supercedes #17811 to merge it

Thanks a ton @noname0310

[sebavan]

/azp run

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[sebavan]

/azp run

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[bjsplat]

Please make sure to label your PR with "bug", "new feature" or "breaking change" label(s).
To prevent this PR from going to the changelog marked it with the "skip changelog" label.

[bjsplat]

Snapshot stored with reference name:
refs/pull/17829/merge

Test environment:
https://snapshots-cvgtc2eugrd3cgfd.z01.azurefd.net/refs/pull/17829/merge/index.html

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

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[bjsplat]

Interaction tests

https://snapshots-cvgtc2eugrd3cgfd.z01.azurefd.net/refs/pull/17829/merge/testResults/interactionplaywright/index.html

[bjsplat]

Visualization tests for WebGPU

https://snapshots-cvgtc2eugrd3cgfd.z01.azurefd.net/refs/pull/17829/merge/testResults/webgpuplaywright/index.html

[bjsplat]

WebGL2 visualization test reporter:

https://snapshots-cvgtc2eugrd3cgfd.z01.azurefd.net/refs/pull/17829/merge/testResults/webgl2playwright/index.html

[bjsplat]

Devhost visualization test reporter:

https://snapshots-cvgtc2eugrd3cgfd.z01.azurefd.net/refs/pull/17829/merge/testResults/devhostplaywright/index.html