[clang] [HLSL] Make sure `isSigned` flag is set on target type for `TypedBuffer` resources with signed int vectors (PR #130223)

[Joshua Batista via cfe-commits]

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

LGTM for DXIL. Is there a plan to do this with SPIR-V too?

https://github.com/llvm/llvm-project/pull/130223