C#: Add model generator test cases with in/out parameters.

Author: michaelnebel

csharp/ql/test/utils/modelgenerator/dataflow/CaptureContentSummaryModels.expected

@@ -1,2 +1,4 @@
 unexpectedModel
+| Unexpected contentbased-summary found: Models;ParameterModifiers;false;Copy;(System.Object,System.Object);;Argument[0];ReturnValue;value;dfc-generated |
 expectedModel
+| Expected contentbased-summary missing: Models;ParameterModifiers;false;Copy;(System.Object,System.Object);;Argument[0];Argument[1];value;dfc-generated |

csharp/ql/test/utils/modelgenerator/dataflow/CaptureSummaryModels.expected

@@ -1,2 +1,4 @@
 unexpectedModel
+| Unexpected summary found: Models;ParameterModifiers;false;Copy;(System.Object,System.Object);;Argument[0];ReturnValue;taint;df-generated |
 expectedModel
+| Expected summary missing: Models;ParameterModifiers;false;Copy;(System.Object,System.Object);;Argument[0];Argument[1];taint;df-generated |

csharp/ql/test/utils/modelgenerator/dataflow/Summaries.cs

@@ -1034,3 +1034,27 @@ public override object GetValue()
         }
     }
 }
+
+public class ParameterModifiers
+{
+    // contentbased-summary=Models;ParameterModifiers;false;Copy;(System.Object,System.Object);;Argument[0];Argument[1];value;dfc-generated
+    // summary=Models;ParameterModifiers;false;Copy;(System.Object,System.Object);;Argument[0];Argument[1];taint;df-generated
+    public void Copy(object key, out object value)
+    {
+        value = key;
+    }
+
+    // contentbased-summary=Models;ParameterModifiers;false;CopyToRef;(System.Object,System.Object);;Argument[0];Argument[1];value;dfc-generated
+    // summary=Models;ParameterModifiers;false;CopyToRef;(System.Object,System.Object);;Argument[0];Argument[1];taint;df-generated
+    public void CopyToRef(object key, ref object value)
+    {
+        value = key;
+    }
+
+    // contentbased-summary=Models;ParameterModifiers;false;InReturn;(System.Object);;Argument[0];ReturnValue;value;dfc-generated
+    // summary=Models;ParameterModifiers;false;InReturn;(System.Object);;Argument[0];ReturnValue;taint;df-generated
+    public object InReturn(in object v)
+    {
+        return v;
+    }
+}