KT-5492 J2K: convert field with getter/setter to property

#KT-5492 Fixed

j2k/tests/testData/ast/dropAccessors/CannotDropOnlySetter.kt

@@ -0,0 +1,7 @@
+public class AAA {
+    private var x = 42
+
+    public fun setX(x: Int) {
+        this.x = x
+    }
+}