Kotlin: Add test for missing kotlin to java property mapping

java/ql/test/kotlin/library-tests/java-map-methods/test.expected

@@ -1,2 +1,5 @@
+diagnostics
+| file://:0:0:0:0 | Couldn't find a Java equivalent function to kotlin.String.<get-length> in java.lang.String |
+#select
 | Integer |
 | Object |

java/ql/test/kotlin/library-tests/java-map-methods/test.kt

@@ -1 +1,3 @@
 fun test(m: Map<Int, Int>) = m.getOrDefault(1, 2)
+
+fun test2(s: String) = s.length

java/ql/test/kotlin/library-tests/java-map-methods/test.ql

@@ -1,4 +1,7 @@
 import java
+import semmle.code.java.Diagnostics
 
 from MethodAccess ma
 select ma.getCallee().getAParameter().getType().toString()
+
+query predicate diagnostics(Diagnostic d) { any() }