Merge LTC and DFG LUTs into a texture array

[beicause]

Objective

Reduce texture bindings in mesh view bind group.

Solution

Merge LTC and DFG LUTs into a texture array and remove dfg_lut feature.

Since #23288 adds luts, bevy_pbr should enable bevy_image/ktx2 and bevy_image/zstd.

The ltc_dfg.ktx2 is created using KTX-Sofeware, DFG lut is converted from Rg16Float to Rgba16Float:

ktx extract ltc1.ktx2 ltc1.exr
ktx extract ltc2.ktx2 ltc2.exr
ktx extract dfg.ktx2 dfg.exr
ktx create --format R16G16B16A16_SFLOAT --layers 3 --zstd 22 ltc1.exr ltc2.exr dfg.exr ltc_dfg.ktx2

Testing

Run testbed_3d. Solari is untested.

[github-actions]

Your PR caused a change in the graphical output of an example or rendering test. This might be intentional, but it could also mean that something broke!
You can review it at https://pixel-eagle.com/project/B04F67C0-C054-4A6F-92EC-F599FEC2FD1D?filter=PR-24004

If it's expected, please add the M-Deliberate-Rendering-Change label.

If this change seems unrelated to your PR, you can consider updating your PR to target the latest main branch, either by rebasing or merging main into it.

[github-actions]

Your PR caused a change in the graphical output of an example or rendering test. This might be intentional, but it could also mean that something broke!
You can review it at https://pixel-eagle.com/project/B04F67C0-C054-4A6F-92EC-F599FEC2FD1D?filter=PR-24004

If it's expected, please add the M-Deliberate-Rendering-Change label.

If this change seems unrelated to your PR, you can consider updating your PR to target the latest main branch, either by rebasing or merging main into it.

[beicause]

Do we want to keep the dfg_lut feature and also gate ltc luts (for rect light) behind a feature flag #23737 (comment)? If so we should only convert the 2 ltc luts into a texture array.

Edit: If we decide replace point light implementation with ltc #23400, then we should not gate ltc otherwise neither point light nor rect light can be used.

[kfc35]

This PR, after having main merged into it, currently fixes #23975 for me (since it reduces the number of SampledTextures)

However, since it’s still a WIP, I won’t place it into the milestone yet until I reconfirm after it is back to being ready for review (Although I think putting back the feature gating will still keep the sampledTextures number lower than the limit?)

[beicause]

I prefer #24065 to gate ltc luts.