[llvm] [IRLinker] Don't add duplicate named MD node operand to dest module (PR #146020)

[Matt Arsenault via llvm-commits]

arsenm wrote:

Can you add tests that cover the behavior for these other nodes: https://github.com/llvm/llvm-project/blob/60a18d611907dc904cd893a53c72b99c8e55ae06/llvm/lib/Target/AMDGPU/AMDGPUUnifyMetadata.cpp#L26

I'm not sure if we should opt in for specific named metadata 

https://github.com/llvm/llvm-project/pull/146020