[DirectX] Add Root Descriptor element support to obj2yaml/yaml2obj

[joaosaffran]

Obj2yaml and yaml2obj need to support Root Descriptor parameters.

AC:

• Add support for required flags in DXContainer.h.
• Add the parameter and it's properties to MC/DXContainerRootSignature.h.
• Add the parameter and it's properties to Object/DXContainer.h.
• Add support for the yaml parser in DXContainerYAML.h, llvm/lib/ObjectYAML/DXContainerEmitter.cpp and DXContainerYAML.cpp.
• Add binary writing support in MC/DXContainerRootSignature.cpp.
• Add parsing logic in llvm/lib/Object/DXContainer.cpp.
• Add unit test using DXC generated binaries in DXContainerTest.cpp and DXContainerYAMLTest.cpp.
• Add round trip unit test.