Validator does not check Scope id argument of OpGroupNonUniform instructions correctly.

[SPIRV spec](https://www.khronos.org/registry/spir-v/specs/unified1/SPIRV.html#_a_id_shadervalidation_a_validation_rules_for_shader_a_href_capability_capabilities_a) says "All _\_ used for **Scope** and Memory Semantics must be of an **OpConstant**.", but SPIRV Validator does not check the _Scope \_ argument of OpGroupNonUniform instructions correctly.

In the following code, `%24 = OpGroupNonUniformBallot %v4uint %19 %true` is not valid. `%19` must be a `OpConstant`.

```
; SPIR-V
; Version: 1.3
; Generator: Khronos Glslang Reference Front End; 7
; Bound: 34
; Schema: 0
OpCapability Shader
OpCapability GroupNonUniform
OpCapability GroupNonUniformBallot
%1 = OpExtInstImport "GLSL.std.450"
OpMemoryModel Logical GLSL450
OpEntryPoint GLCompute %main "main"
OpExecutionMode %main LocalSize 128 1 1
OpSource GLSL 450
OpSourceExtension "GL_KHR_shader_subgroup_ballot"
OpSourceExtension "GL_KHR_shader_subgroup_basic"
OpName %main "main"
OpName %layout_result "layout_result"
OpMemberName %layout_result 0 "result"
OpName %_ ""
OpName %layout_foo "layout_foo"
OpMemberName %layout_foo 0 "foo"
OpName %__0 ""
OpDecorate %_runtimearr_float ArrayStride 4
OpMemberDecorate %layout_result 0 Offset 0
OpDecorate %layout_result BufferBlock
OpDecorate %_ DescriptorSet 0
OpDecorate %_ Binding 1
OpMemberDecorate %layout_foo 0 Offset 0
OpDecorate %layout_foo BufferBlock
OpDecorate %__0 DescriptorSet 0
OpDecorate %__0 Binding 0
OpDecorate %gl_WorkGroupSize BuiltIn WorkgroupSize
%void = OpTypeVoid
%3 = OpTypeFunction %void
%float = OpTypeFloat 32
%_runtimearr_float = OpTypeRuntimeArray %float
%layout_result = OpTypeStruct %_runtimearr_float
%_ptr_Uniform_layout_result = OpTypePointer Uniform %layout_result
%_ = OpVariable %_ptr_Uniform_layout_result Uniform
%int = OpTypeInt 32 1
%int_0 = OpConstant %int 0
%uint = OpTypeInt 32 0
%layout_foo = OpTypeStruct %uint
%_ptr_Uniform_layout_foo = OpTypePointer Uniform %layout_foo
%__0 = OpVariable %_ptr_Uniform_layout_foo Uniform
%_ptr_Uniform_uint = OpTypePointer Uniform %uint
%bool = OpTypeBool
%true = OpConstantTrue %bool
%v4uint = OpTypeVector %uint 4
%uint_3 = OpConstant %uint 3
%uint_0 = OpConstant %uint 0
%_ptr_Uniform_float = OpTypePointer Uniform %float
%v3uint = OpTypeVector %uint 3
%uint_128 = OpConstant %uint 128
%uint_1 = OpConstant %uint 1
%gl_WorkGroupSize = OpConstantComposite %v3uint %uint_128 %uint_1 %uint_1
%main = OpFunction %void None %3
%5 = OpLabel
%18 = OpAccessChain %_ptr_Uniform_uint %__0 %int_0
%19 = OpLoad %uint %18
%24 = OpGroupNonUniformBallot %v4uint %19 %true
%26 = OpCompositeExtract %uint %24 0
%27 = OpConvertUToF %float %26
%29 = OpAccessChain %_ptr_Uniform_float %_ %int_0 %19
OpStore %29 %27
OpReturn
OpFunctionEnd
```

Start with the SPIR-V validator's handling of OpGroupNonUniform instructions and reproduce the issue using the assembly in this report. Trace validation of the Scope operand and add coverage showing that a loaded value such as %19 is rejected while an OpConstant is accepted.

Written by the indexing model from the issue text.