Improve handling of texture names in glTF loader

[bghgary]

See https://forum.babylonjs.com/t/gltfloader-option-to-keep-or-prefer-original-texture-or-image-name-as-name-of-loaded-texture/37307

Tested with this PG: http://localhost:1338/#SJUH9H#3

[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/15709/merge

Test environment:
https://snapshots-cvgtc2eugrd3cgfd.z01.azurefd.net/refs/pull/15709/merge/index.html

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

https://snapshots-cvgtc2eugrd3cgfd.z01.azurefd.net/refs/pull/15709/merge/index.html#WGZLGJ#4600

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https://playground.babylonjs.com/?snapshot=refs/pull/15709/merge
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To test the snapshot in the playground with a playground ID add it after the snapshot query string:

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[bjsplat]

Visualization tests for WebGPU (Experimental)

https://snapshots-cvgtc2eugrd3cgfd.z01.azurefd.net/refs/pull/15709/merge/testResults/webgpuplaywright/index.html

[bjsplat]

WebGL2 visualization test reporter:

https://snapshots-cvgtc2eugrd3cgfd.z01.azurefd.net/refs/pull/15709/merge/testResults/webgl2playwright/index.html

[bghgary]

@Popov72 @sebavan I've update the PR with some code to serialize the label property but it's not perfect because the code is storing the label of InternalTexture on Texture instead since we don't serialize InternalTexture. This has potential for conflicts and more bytes serialized than necessary, but it's unlikely to cause a problem.