jit-diff: improve reconciliation when there are multiple methods with the same name

See dotnet/coreclr#14244 -- the "savings" seen here is misleading:
```
-516 : System.Private.CoreLib.dasm - InterfaceIsCheckWorkaround`1:.cctor() (7 methods)
```
The diff version had only 3 of the 7 copies -- the other 4 instantations were no longer needed because of changes in codegen in other methods.

Reconciliation should have noted that the base version had 4 extra methods instead of making it look like both versions had these 7 methods and they shrank a lot.