C#: Add lambda attributes test cases.

Author: michaelnebel

csharp/ql/test/library-tests/csharp10/lambdaAttributes.expected

@@ -0,0 +1,7 @@
+allAttributes
+| LambdaAttributes.cs:14:20:14:26 | [Example(...)] | LambdaAttributes.cs:14:28:14:28 | 1 | Parameter |
+| LambdaAttributes.cs:15:18:15:24 | [Example(...)] | LambdaAttributes.cs:15:26:15:26 | 2 | LambdaExpr |
+| LambdaAttributes.cs:16:26:16:32 | [return: Example(...)] | LambdaAttributes.cs:16:34:16:34 | 3 | LambdaExpr |
+lambdaAttributes
+| LambdaAttributes.cs:15:18:15:24 | [Example(...)] | LambdaAttributes.cs:15:26:15:26 | 2 | LambdaAttributes.cs:15:17:15:52 | (...) => ... |
+| LambdaAttributes.cs:16:26:16:32 | [return: Example(...)] | LambdaAttributes.cs:16:34:16:34 | 3 | LambdaAttributes.cs:16:17:16:60 | (...) => ... |

csharp/ql/test/library-tests/csharp10/lambdaAttributes.ql

@@ -0,0 +1,11 @@
+import csharp
+
+query predicate allAttributes(Attribute a, Expr arg, string c) {
+  a.fromSource() and
+  arg = a.getArgument(0) and
+  c = a.getTarget().(Element).getAPrimaryQlClass()
+}
+
+query predicate lambdaAttributes(Attribute a, Expr arg, LambdaExpr l) {
+  allAttributes(a, arg, _) and a.getTarget() = l
+}