Synthetic properties: correct behaviour for method hierarchies

compiler/testData/codegen/boxAgainstJava/syntheticExtensions/overrideOnlyGetter.java

@@ -0,0 +1,10 @@
+class JavaClass1 {
+    protected Object value = null;
+
+    public Object getSomething() { return null; }
+    public void setSomething(Object value) {  this.value = value; }
+}
+
+class JavaClass2 extends JavaClass1 {
+    public String getSomething() { return (String)value; }
+}

compiler/testData/codegen/boxAgainstJava/syntheticExtensions/overrideOnlyGetter.kt

@@ -0,0 +1,5 @@
+fun box(): String {
+    val javaClass = JavaClass2()
+    javaClass.something = "OK"
+    return javaClass.something
+}