Minor, improve test on unexported package in Java module

Add Kotlin class/function/property.

compiler/testData/javaModules/simpleUseNonExportedPackage/moduleA/a/K.kt

@@ -0,0 +1,9 @@
+package a
+
+import a.impl.KImpl
+
+open class K {
+    companion object {
+        fun getInstance(): KImpl = KImpl()
+    }
+}

compiler/testData/javaModules/simpleUseNonExportedPackage/moduleA/a/impl/AImpl.java

@@ -2,4 +2,7 @@ package a.impl;
 
 import a.A;
 
-public class AImpl extends A {}
+public class AImpl extends A {
+    public static String field = "";
+    public static String method() { return ""; }
+}

compiler/testData/javaModules/simpleUseNonExportedPackage/moduleA/a/impl/KImpl.kt

@@ -0,0 +1,10 @@
+package a.impl
+
+import a.K
+
+class KImpl : K() {
+    companion object {
+        val field: String = ""
+        fun method(): String = ""
+    }
+}

compiler/testData/javaModules/simpleUseNonExportedPackage/moduleA/a/impl/KotlinFile.kt

@@ -0,0 +1,4 @@
+package a.impl
+
+val fileField: String = ""
+fun fileMethod(): String = ""

compiler/testData/javaModules/simpleUseNonExportedPackage/moduleA/module-info.java

@@ -1,3 +1,5 @@
 module moduleA {
     exports a;
+
+    requires kotlin.stdlib;
 }