[llvm] [DirectX] Implement the DXILCBufferAccess pass (PR #134571)

[Steven Perron via llvm-commits]

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s-perron wrote:

Is this the right place for this transformation? I expect that we would want this pass to run for all backends. We would definitely want it for SPIR-V. Could we move it into an HLSL directory as in https://github.com/llvm/llvm-project/pull/134260?

https://github.com/llvm/llvm-project/pull/134571