backing fields resolve changed

KT-462 Consider allowing initializing properties via property names when it is safe
KT-598 Allow to use backing fields after this expression

compiler/testData/diagnostics/tests/backingField/ReadNonexistentDeclaredInHigher.jet

@@ -1,7 +1,6 @@
-val y = 1
-
-class A() {
-    {
-        val x = <!UNRESOLVED_REFERENCE!>$y<!>
-    }
-}
+class CustomValNoBackingField() {
+    val a: Int
+        get() = 1
+    
+    val b = <!NO_BACKING_FIELD_CUSTOM_ACCESSORS!>$a<!>
+}