Add two VkPhysicalDevicePortabilitySubsetFeaturesKHR::borderColorOpaqueBlack* capabilities

Sampler border color opaque black `(0.0, 0.0, 0.0, 1.0)` appears as transparent red `(1.0, 0.0, 0.0, 0.0)` for formats `R4G4B4A4_UNORM_PACK16` or `R5G5B5A1_UNORM_PACK16`

This appears to be a Metal limitation or bug.

This affects the following 66 CTS tests:

```
dEQP-VK.pipeline.sampler.view_type.*.format.b4g4r4a4_unorm_pack16.address_modes.all_mode_clamp_to_border_opaque_black
dEQP-VK.pipeline.sampler.view_type.*.format.r4g4b4a4_unorm_pack16.address_modes.all_mode_clamp_to_border_opaque_black
dEQP-VK.pipeline.sampler.view_type.*.format.r5g5b5a1_unorm_pack16.address_modes.all_mode_clamp_to_border_opaque_black
dEQP-VK.pipeline.sampler.border_swizzle.b4g4r4a4_unorm_pack16.*.opaque_black
dEQP-VK.pipeline.sampler.border_swizzle.r4g4b4a4_unorm_pack16.*.opaque_black
dEQP-VK.pipeline.sampler.border_swizzle.r5g5b5a1_unorm_pack16.*.opaque_black
```

Recommend adding the following capabilities, and testing for them within CTS on the above tests:

```
VkPhysicalDevicePortabilitySubsetFeaturesKHR::borderColorOpaqueBlackB4G4R4A4
VkPhysicalDevicePortabilitySubsetFeaturesKHR::borderColorOpaqueBlackR4G4B4A4
VkPhysicalDevicePortabilitySubsetFeaturesKHR::borderColorOpaqueBlackR5G5B5A1
```

Start by locating the VkPhysicalDevicePortabilitySubsetFeaturesKHR feature definition and the listed CTS sampler tests. Verify how existing portability-subset capabilities are represented and tested, then determine the corresponding CTS expectations for the three opaque-black cases. Done means the capabilities are defined and the affected tests can check them.

Written by the indexing model from the issue text.