C#: Use fully qualified name with types instead of label in IR queries.

Author: michaelnebel

csharp/ql/src/experimental/ir/internal/IRCSharpLanguageDebug.qll

@@ -2,4 +2,4 @@ private import csharp as CSharp
 
 class Function = CSharp::Callable;
 
-string getIdentityString(Function func) { result = func.getLabel() }
+string getIdentityString(Function func) { result = func.getFullyQualifiedNameWithTypes() }