KT-12152 : constructor consistency: distinguish properties with and w/o backing fields, with default / custom accessors

compiler/testData/diagnostics/tests/constructorConsistency/getset.kt

@@ -0,0 +1,17 @@
+class My(var x: String) {
+
+    var y: String
+        get() = if (x != "") x else z
+        set(arg) {
+            if (arg != "") x = arg
+        }
+
+    val z: String
+
+    init {
+        // Dangerous: setter!
+        <!DEBUG_INFO_LEAKING_THIS!>y<!> = "x"
+        // Dangerous: getter!
+        if (<!DEBUG_INFO_LEAKING_THIS!>y<!> != "") z = this.<!DEBUG_INFO_LEAKING_THIS!>y<!> else z = <!DEBUG_INFO_LEAKING_THIS!>y<!>
+    }
+}