[clang] [HLSL] Add Append/ConsumeStructuredBuffer definitions to HLSLExternalSemaSource (PR #113643)

[Joshua Batista via cfe-commits]

https://github.com/bob80905 approved this pull request.

My other comment is just a nit, I can approve this as it is.

https://github.com/llvm/llvm-project/pull/113643