Swift: add AnnotatedExitNode to cfg to match prior interface

Author: rdmarsh2

swift/ql/lib/codeql/swift/controlflow/CfgNodes.qll

@@ -145,4 +145,6 @@ class KeyPathExprCfgNode extends ExprCfgNode {
 
 class EntryNode = Impl::EntryNode;
 
-class ExitNode = Impl::ExitNode;
+class ExitNode = Impl::ExitNode;
+
+class AnnotatedExitNode = Impl::AnnotatedExitNode;