Add extra test for collection initialization

Author: tamasvajk

csharp/ql/test/library-tests/csharp9/AnonymousObjectCreation.cs

@@ -19,4 +19,9 @@ public AnonObj M1(AnonObj t)
     void M2(int x) { }
 
     D GetM() { return new(M2); }
+
+    void MethodAdd()
+    {
+        List<int> list = new();// { 1, 2, 3 }; todo: the initializer causes an extraction error
+    }
 }

csharp/ql/test/library-tests/csharp9/AnonymousObjectCreation.expected

@@ -2,5 +2,6 @@ implicitlyTypedObjectCreation
 | AnonymousObjectCreation.cs:7:31:7:35 | object creation of type List<AnonObj> |
 | AnonymousObjectCreation.cs:13:17:13:35 | object creation of type AnonObj |
 | AnonymousObjectCreation.cs:14:16:14:20 | object creation of type AnonObj |
+| AnonymousObjectCreation.cs:25:26:25:30 | object creation of type List<Int32> |
 implicitlyTypedDelegateCreation
 | AnonymousObjectCreation.cs:21:23:21:29 | delegate creation of type D |

csharp/ql/test/library-tests/csharp9/PrintAst.expected

@@ -45,6 +45,15 @@ AnonymousObjectCreation.cs:
 #   21|         0: [ExplicitDelegateCreation] delegate creation of type D
 #   21|           0: [ImplicitDelegateCreation] delegate creation of type D
 #   21|             0: [MethodAccess] access to method M2
+#   23|   11: [Method] MethodAdd
+#   23|     -1: [TypeMention] Void
+#   24|     4: [BlockStmt] {...}
+#   25|       0: [LocalVariableDeclStmt] ... ...;
+#   25|         0: [LocalVariableDeclAndInitExpr] List<Int32> list = ...
+#   25|           -1: [TypeMention] List<Int32>
+#   25|             1: [TypeMention] int
+#   25|           0: [LocalVariableAccess] access to local variable list
+#   25|           1: [ObjectCreation] object creation of type List<Int32>
 Discard.cs:
 #    3| [Class] Discard
 #    5|   5: [Method] M1