[llvm] [GVN] Decouple GVNValueTable and GVNPass (NFC) (PR #226232)

[Antonio Frighetto via llvm-commits]

================
@@ -116,6 +116,84 @@ struct GVNOptions {
   }
 };
 
+/// A mapping from value numbers to lists of Value*'s that
+/// have that value number.  Use findLeader to query it.
----------------
antoniofrighetto wrote:

```suggestion
/// have that value number. Use getLeaders to query it.
```

https://github.com/llvm/llvm-project/pull/226232