[HLSL] Adding support for root descriptors in root signature metadata representation (#139781)
- adds parsing from metadata into dxcontainer binary
- adds validations as described in the spec
- adds testing scenarios
closes: [#126638](https://github.com/llvm/llvm-project/issues/126638)
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Co-authored-by: joaosaffran <joao.saffran@microsoft.com>