Differ this/non-this instances for vars initialization in class

When deal with constructed object (not this) treat it like it's fully initialized.

Otherwise (this or access with no receiver) access instruction
should be handled as it was before.

 #KT-6788 Fixed
 #KT-4126 Fixed

compiler/testData/diagnostics/tests/controlFlowAnalysis/propertiesInitWithOtherInstance.txt

@@ -0,0 +1,10 @@
+package
+
+internal final class A {
+    public constructor A(/*0*/ next: A? = ...)
+    internal final val next: A?
+    internal final val x: kotlin.String
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}