Deprecate loadCRN and loadKTX

[ebogo1]

This deprecates loadCRN and loadKTX as we will move to support KTX2 in Cesium 1.82.

[cesium-concierge]

Thanks for the pull request @ebogo1!

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[lilleyse]

Just noting here that once we remove loadCRN and loadKTX we will need to

• Update the Image-Based Lighting sandcastle
• Update the Materials sandcastle

Both of these use KTX textures

[ebogo1]

@lilleyse I updated the deprecation warning wordings in 37130dd.

Just noting here that once we remove loadCRN and loadKTX we will need to

I also opened #9479 to keep track of the KTX2 to-do list.

[lilleyse]

I pushed some tweaks to CHANGES.md above. Otherwise looks good. Merging since CI passed on the last code changes, my changes were just CHANGES.md.

[mramato]

@lilleyse @ebogo1 Why did we deprecate loadKtx but keep it's Sandcastle example? If something is deprecated it shouldn't be used anywhere in the examples.

[mramato]

It's in both the Materials and Image Based Lighting demos.

[ebogo1]

One option is to roll back the deprecation warnings and add them as part of the KTX2 PR. If delaying that PR by adding back loadKTX/CRN isn't worth it, maybe we can just remove the "compressed image" option from Materials and use a non-ktx file in Image-Based Lighting for now?

Both Sandcastles are using KTX 2.0 in the new PR.

[mramato]

I think the main reason we wanted to deprecate was because no one as far as we know is actually using old KTX and it was easier to make a clean break. If the Sandcastle examples are just updated to use KTX2 in your PR, then it would be silly to remove them and then re-add them..

Both Sandcastles are specific to compressed textures, I believe, so we can't really make them use something else (and it's probably not worth it).

[mramato]

Okay, since @lilleyse is MIA, I'm going to just proceed as things currently are. We want to drop CRN/KTX asap so getting the notice in now is probably the best choice.

[lilleyse]

I think it's fine to proceed. There's no way to remove KTX1 support from the Image-Based Lighting sandcastle without breaking it before KTX2 is in.

The other approach could have been to add KTX2 and in the same PR have an immediate breaking change for CRN/KTX1, but that doesn't give as much warning.