Add support for UASTC decoding

[Erik-White]

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• I have written a descriptive pull-request title
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• I have provided test coverage for my change (where applicable)

Description

UASTC ("Universal ASTC") is a block format from Basis Universal
It is a constrained subset of LDR ASTC 4×4. Every UASTC block maps to a legal ASTC 4×4 block, and the conversion is lossless. But the two are not bit-compatible.

Our overall goal is to simplify the encoding and efficient distribution of portable LDR and HDR GPU texture, image, and short animated texture content in a way that is compatible with any GPU, rendering/graphics API, or platform including plain WASM.

This PR implements support by reusing the existing ASTC implementation. A couple of sections have been broken out to allow re-use but otherwise the existing pipeline can be used as-is.

[Erik-White]

I realize that there is ongoing work to rewrite the entire library, so I understand that this might have to wait - and maybe need some rewriting if the rewrite lands first :)

[JimBobSquarePants]

@Erik-White if you update this from main and fix any required changes I’ll merge it so you are unblocked

[Erik-White]

Fantastic! I rebased onto main

[Erik-White]

I also opened a PR in SharedInfrastucture to properly add the UASTC and RAW file types so they can be used in test data