spv::CapabilityGroups isn't supported

VK_AMD_shader_ballot adds support for SPV_AMD_shader_ballot, which adds 'OpCapability Groups' and a bunch of OpGroup-instructions.

Feeding spirv code to vkCreateComputePipelines with 'Capability Groups' result in the validation error below. It says 'Unhandled OpCapability' since 'groups' is missing from string_SpvCapability(spirv_validation_helper.cpp::347). I checked in debugger that it was capability 18. Validation fails in CoreChecks::ValidateShaderCapabilitiesAndExtensions because 'groups' doesn't exist in the spirvCapabilities map.

Validation Error: [ VUID-VkShaderModuleCreateInfo-pCode-01090 ] Object 0: handle = 0x7ff84b0, type = VK_OBJECT_TYPE_DEVICE; | MessageID = 0x2c00a3d6 | vkCreateShaderModule(): A SPIR-V Capability (Unhandled OpCapability) was declared that is not supported by Vulkan. The Vulkan spec states: pCode must not declare any capability that is not supported by the API, as described by the Capabilities section of the SPIR-V Environment appendix (https://vulkan.lunarg.com/doc/view/1.2.198.1/windows/1.2-extensions/vkspec.html#VUID-VkShaderModuleCreateInfo-pCode-01090)

Spirv-disassembly:
[CP_BallotTest_00000000_00000001.txt](https://github.com/KhronosGroup/Vulkan-ValidationLayers/files/7901133/CP_BallotTest_00000000_00000001.txt)

I'm running on a Radeon Vega64, 1.2.198.1 SDK.

Extensions enabled:
Id: 2df0 23:51:56.936 | vkCreateDevice with extensions:
Id: 2df0 23:51:56.936 | VK_KHR_swapchain
Id: 2df0 23:51:56.936 | VK_KHR_shader_draw_parameters
Id: 2df0 23:51:56.936 | VK_EXT_shader_viewport_index_layer
Id: 2df0 23:51:56.936 | VK_EXT_shader_subgroup_ballot
Id: 2df0 23:51:56.936 | VK_AMD_gcn_shader
Id: 2df0 23:51:56.936 | VK_AMD_shader_ballot
Id: 2df0 23:51:56.936 | VK_AMD_draw_indirect_count
Id: 2df0 23:51:56.936 | VK_AMD_rasterization_order
Id: 2df0 23:51:56.936 | VK_AMD_shader_info