[llvm] [SandboxIR] Add setOperand() and RAUW,RUWIf,RUOW (PR #98410)

[Arthur Eubanks via llvm-commits]

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@@ -303,6 +309,13 @@ class Value {
 #endif
 };
 
+/// Helper Attorney-Client class that gives access to the underlying IR.
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aeubanks wrote:

can we add `friend class User;` in `Value` instead?

https://github.com/llvm/llvm-project/pull/98410