C#/Java: Add some dfc-generated test cases.

java/ql/test/library-tests/dataflow/external-models/C.java

@@ -54,6 +54,8 @@ public class C {
     // The summary for the parameter is ignored, because it is generated and
     // because there is a manual neutral summary model for this callable.
     lib.apiStepArgQualGeneratedIgnored(arg1);
+
+    lib.getValue();
   }
 
   void fooPossibleLibraryDispatch(Library lib) {

java/ql/test/library-tests/dataflow/external-models/steps.expected

@@ -11,4 +11,5 @@ invalidModelRow
 | C.java:44:32:44:35 | arg1 | C.java:44:5:44:36 | apiStepArgResGenerated(...) |
 | C.java:50:45:50:48 | arg2 | C.java:50:5:50:49 | apiStepArgResGeneratedIgnored(...) |
 | C.java:52:33:52:36 | arg1 | C.java:52:5:52:7 | lib [post update] |
-| C.java:62:12:62:15 | arg1 | C.java:62:5:62:16 | id(...) |
+| C.java:58:5:58:7 | lib | C.java:58:5:58:18 | getValue(...) |
+| C.java:64:12:64:15 | arg1 | C.java:64:5:64:16 | id(...) |

java/ql/test/library-tests/dataflow/external-models/steps.ext.yml

@@ -16,6 +16,7 @@ extensions:
       - ["my.qltest.external", "Library", False, "apiStepArgQualGenerated", "(Object)", "", "Argument[0]", "Argument[this]", "taint", "df-generated"]
       - ["my.qltest.external", "Library", False, "apiStepArgQualGeneratedIgnored", "(Object)", "", "Argument[0]", "Argument[this]", "taint", "df-generated"]
       - ["my.qltest.external", "Library", False, "id", "(Object)", "", "Argument[0]", "ReturnValue", "taint", "df-generated"]
+      - ["my.qltest.external", "Library", False, "getValue", "()", "", "Argument[this]", "ReturnValue", "taint", "dfc-generated"]
   - addsTo:
       pack: codeql/java-all
       extensible: neutralModel

java/ql/test/library-tests/dataflow/external-models/stubs/Library.java

@@ -20,4 +20,8 @@ public class Library {
   public Object id(Object x) {
     return null;
   }
+
+  public Object getValue() {
+    return null;
+  }
 }