[HLSL] HLSLResourceBindingAttr is not added to numeric `$Globals` default constant declarations

[hekota]

register(c#) annotations on numeric constants in the global scope are not translated to HLSLResourceBindingAttr. This applies to scalar, vector and array constants.

For this code:

float a : register(c5);

[numthreads(4,1,1)]
void main() {
}

The AST should contain HLSLResourceBindingAttr added to the VarDecl for 'a' like this:

...
| |-VarDecl 0x#### <line:1:1, col:7> col:7 a 'hlsl_constant float'
| | `-HLSLResourceBindingAttr 0x#### <col:7> "c5" "space0"
...

https://godbolt.org/z/sfEcEEjK4

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Helena Kotas (hekota)

`register(c#`) annotations on numeric constants in the global scope are not translated to `HLSLResourceBindingAttr`. This applies to scalar, vector and array constants.

For this code:

float a : register(c5);

[numthreads(4,1,1)]
void main() {
}

The AST should contain HLSLResourceBindingAttr added to the VarDecl for 'a' like this:

...
| |-VarDecl 0x#### <line:1:1, col:7> col:7 a 'hlsl_constant float'
| | `-HLSLResourceBindingAttr 0x#### <col:7> "c5" "space0"
...

https://godbolt.org/z/sfEcEEjK4