[llvm] [DirectX] Updating DXContainer Yaml to represent Root Signature 1.2 (PR #159659)

[Finn Plummer via llvm-commits]

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inbelic wrote:

Should we also add an equivalent test for invalid sampler flag values?

edit: I guess we haven't added that validation in this pr yet

https://github.com/llvm/llvm-project/pull/159659