Control-Flow: Generate instruction for left-hand side of invalid assignments

#KT-8390 Fixed

compiler/testData/diagnostics/tests/LValueAssignment.kt

@@ -39,7 +39,7 @@ class D() {
 fun foo(): Unit {}
 
 fun cannotBe() {
-    var <!UNUSED_VARIABLE!>i<!>: Int = 5
+    var i: Int = 5
 
     <!UNRESOLVED_REFERENCE!>z<!> = 30;
     <!VARIABLE_EXPECTED!>""<!> = "";
@@ -135,4 +135,4 @@ fun Array<Int>.checkThis() {
 
 abstract class Ab {
     abstract fun getArray() : Array<Int>
-}
+}