[llvm] [DirectX] adding support in obj2yaml and yaml2obj to root constants (PR #127840)

[via llvm-commits]

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@@ -14,20 +14,18 @@ Parts:
     Size:            24
     RootSignature:
       Version: 2
-      NumParameters: 1
-      RootParametersOffset: 3
       NumStaticSamplers: 4
       StaticSamplersOffset: 5
+      Parameters: []
       AllowInputAssemblerInputLayout: true
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joaosaffran wrote:

There is a test I added here in `llvm/unittests/Object/DXContainerTest.cpp`, that changes the offset to an invalid value. Is that enough? @llvm-beanz 

https://github.com/llvm/llvm-project/pull/127840