ASTC decoding part 5: Decode ASTC compressed KTX1 textures

[Erik-White]

Prerequisites

• I have written a descriptive pull-request title
• I have verified that there are no overlapping pull-requests open
• I have verified that I am following the existing coding patterns and practice as demonstrated in the repository. These follow strict Stylecop rules 👮.
• I have provided test coverage for my change (where applicable)

Description

The third part of ASTC (Adaptive scalable texture compression) decoding. ASTC is used with KTX containers to compress texture data.
This adds the full decoding and routing path for ASTC compressed KTX v1 textures. Includes the required pixel types and handling for various ASTC block sizes.

Prerequisites

• Test infrastructure improvements and fixes
• Base decoder and LDR support
• High dynamic range support

To follow

• KTX2 support

Test data

Everything used is either created by myself, or sourced from
https://github.com/KhronosGroup/KTX-Software (Apache 2.0 license)
https://github.com/KhronosGroup/KTX-Software-CTS (Apache 2.0 license)
https://github.com/ARM-software/astc-encoder (Apache-2.0 license)