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

[via llvm-commits]

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

Yes we can, and in this case it makes sense to use a friend because the User class is expected to be tightly coupled to the Value class. But for classes that are not as closely related to the IR, like the transaction tracker, it is nicer to use a client-attorney class to restrict access to just the LLVM Value and nothing else. Anyway, I will remove it for now and add it in later.

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