C#: Add tests for names of nested classes

csharp/ql/test/query-tests/Telemetry/LibraryUsage/ExternalLibraryUsage.cs

@@ -25,4 +25,10 @@ public class LibraryUsage
     {
         var guid1 = Guid.Parse("{12345678-1234-1234-1234-123456789012}"); // Has no flow summary
     }
+
+    public void M4()
+    {
+        var d = new Dictionary<string, object>(); // Uninteresting parameterless constructor
+        var e = d.Keys.GetEnumerator().MoveNext(); // Methods on nested classes
+    }
 }

csharp/ql/test/query-tests/Telemetry/LibraryUsage/ExternalLibraryUsage.expected

@@ -1,2 +1,2 @@
 | System | 5 |
-| System.Collections.Generic | 2 |
+| System.Collections.Generic | 5 |

csharp/ql/test/query-tests/Telemetry/LibraryUsage/SupportedExternalTaint.expected

@@ -1 +1,3 @@
 | System.Collections.Generic#List<>.Add(T) | 2 |
+| System.Collections.Generic#Dictionary<,>+KeyCollection.GetEnumerator() | 1 |
+| System.Collections.Generic#Dictionary<,>.get_Keys() | 1 |