Required CTS modifications

This is a list of modifications required to CTS in order to support the `VK_KHR_portability_subset` extension. The individual mods are [posted as issues to the CTS repository](https://github.com/KhronosGroup/VK-GL-CTS/issues?q=is%3Aissue+is%3Aopen+label%3A%22Vulkan+Portability%22), and listed here as a summary for tracking purposes.

In each entry, the CTS Tests Affected is listed for investigative purposes. A single issue may actually affect multiple CTS tests, and all may not be listed here if the expectation is that fixing one should fix them all.

| CTS Issue ID | Subject | CTS Tests Affected |
| :---: |:--- |:--- |
| [GitLab 3545](https://gitlab.khronos.org/Tracker/vk-gl-cts/-/issues/3545) | Change tests using triangle fans to triangle strips when not needed for test | `dEQP-VK.pipeline.multisample_interpolation.reinterpolation_consistency.interpolate_at_centroid`
`dEQP-VK.pipeline.multisample_interpolation.reinterpolation_consistency.interpolate_at_sample`
| |
| [GitLab 3501](https://gitlab.khronos.org/Tracker/vk-gl-cts/-/issues/3501) | `BC7_RGBAUnorm` & `BC7_RGBAUnorm_sRGB` reserved Mode 8 (zeroed low byte) returns alpha 1.0 instead of recommended 0.0 value | `dEQP-VK.texture.compressed.bc7_unorm_block_2d_pot`
`dEQP-VK.texture.compressed.bc7_srgb_block_2d_pot`
`dEQP-VK.texture.compressed.bc7_unorm_block_2d_npot`
`dEQP-VK.texture.compressed.bc7_srgb_block_2d_npot`
`dEQP-VK.texture.compressed_3D.bc7_unorm_block_3d_pot`
`dEQP-VK.texture.compressed_3D.bc7_srgb_block_3d_pot`
`dEQP-VK.texture.compressed_3D.bc7_unorm_block_3d_npot`
`dEQP-VK.texture.compressed_3D.bc7_srgb_block_3d_npot`
| |
| [GitLab 3268](https://gitlab.khronos.org/Tracker/vk-gl-cts/-/issues/3268)
[GitHub 264](https://github.com/KhronosGroup/VK-GL-CTS/issues/264) | `VK_KHR_portability_subset` extension not recognized | `dEQP-VK.info.device_extensions` | |
| [GitLab 3265](https://gitlab.khronos.org/Tracker/vk-gl-cts/-/issues/3265)
[GitHub 282](https://github.com/KhronosGroup/VK-GL-CTS/issues/282) | Need help understanding validations in `dEQP-VK.texture.mipmap*` tests | `dEQP-VK.texture.mipmap*` | |
| Prerequisite for CTS is #31. | Support Portability capability `VkPhysicalDevicePortabilitySubsetFeaturesKHR:: shaderImageGatherExtendedConstOffsets` | `dEQP-VK.glsl.texture_gather.offsets.*` | |
| Prerequisite for CTS is #33. | Support Portability capability `VkPhysicalDevicePortabilitySubsetFeaturesKHR::workgroupMatrices` | `dEQP-VK.memory_model.shared.basic_types.3`
`dEQP-VK.memory_model.shared.basic_types.9`
`dEQP-VK.memory_model.shared.basic_arrays.4`
`dEQP-VK.memory_model.shared.basic_arrays.6`
`dEQP-VK.memory_model.shared.basic_arrays.7`
`dEQP-VK.memory_model.shared.basic_arrays.9`
`dEQP-VK.memory_model.shared.arrays_of_arrays.0`
`dEQP-VK.memory_model.shared.arrays_of_arrays.2`
`dEQP-VK.memory_model.shared.arrays_of_arrays.4`
`dEQP-VK.memory_model.shared.arrays_of_arrays.5`
`dEQP-VK.memory_model.shared.arrays_of_arrays.8`
`dEQP-VK.memory_model.shared.nested_structs.0`
`dEQP-VK.memory_model.shared.nested_structs.1`
`dEQP-VK.memory_model.shared.nested_structs.2`
`dEQP-VK.memory_model.shared.nested_structs.3`
`dEQP-VK.memory_model.shared.nested_structs.5`
`dEQP-VK.memory_model.shared.nested_structs.6`
`dEQP-VK.memory_model.shared.nested_structs.8`
`dEQP-VK.memory_model.shared.nested_structs.9`
`dEQP-VK.memory_model.shared.nested_structs_arrays.0`
`dEQP-VK.memory_model.shared.nested_structs_arrays.1`
`dEQP-VK.memory_model.shared.nested_structs_arrays.2`
`dEQP-VK.memory_model.shared.nested_structs_arrays.3`
`dEQP-VK.memory_model.shared.nested_structs_arrays.4`
`dEQP-VK.memory_model.shared.nested_structs_arrays.6`
`dEQP-VK.memory_model.shared.nested_structs_arrays.7`
`dEQP-VK.memory_model.shared.nested_structs_arrays.9` | |
| **_Fixed_**
~~[GitLab 3267](https://gitlab.khronos.org/Tracker/vk-gl-cts/-/issues/3267)
[GitHub 281](https://github.com/KhronosGroup/VK-GL-CTS/issues/281)~~ | ~~`VkPhysicalDeviceFeatures::robustBufferAccess` is not a required feature~~ | ~~`dEQP-VK.robustness.*`~~ | |
| **_Fixed_**
~~[GitLab 3266](https://gitlab.khronos.org/Tracker/vk-gl-cts/-/issues/3266)
[GitHub 285](https://github.com/KhronosGroup/VK-GL-CTS/issues/285)~~ | ~~`VK_KHR_portability_subset` extension: Avoid use of triangle fans when not necessary for a test~~ | ~~`dEQP-VK.pipeline.push_constant.graphics_pipeline.overwrite`
`dEQP-VK.pipeline.extended_dynamic_state.*`
`dEQP-VK.pipeline.bind_point.graphics_compute.write_write.*`~~ | |

Start by reviewing the linked VK-GL-CTS issues and the listed CTS test names, then check the prerequisite issues #31 and #33. This tracking issue is done when the individual portability-subset modifications and their prerequisites are resolved, including the still-open entries in the summary.

Written by the indexing model from the issue text.