[clang] [llvm] [clang][SPIR-V] Implement -fspv-preserve-interface (PR #196404)

[Steven Perron via llvm-commits]

s-perron wrote:

@dnovillo Can you take ownership of the corresponding issue, and provide a justification for the option? I forget why we needed it in DXC. Was it a Vulkan validation issue to avoid warnings for mismatches between stages? If we carry an option forward, I would like to make sure the reason for it is still valid. I had opened the issue as a placeholder with the intent of determining if it was still useful. I should have made that more explicit.

https://github.com/llvm/llvm-project/pull/196404