Add annotation tests for schema interface

test/annotations.capnp

@@ -0,0 +1,15 @@
+@0xfb9a160831eee9bb;
+
+struct AnnotationStruct {
+  test @0: Int32;
+}
+
+annotation test1(*): Text;
+annotation test2(*): AnnotationStruct;
+annotation test3(*): List(AnnotationStruct);
+
+$test1("TestFile");
+
+struct TestAnnotationOne $test1("Test") { }
+struct TestAnnotationTwo $test2(test = 100) { }
+struct TestAnnotationThree $test3([(test=100), (test=101)]) { }