CFA merge for definition / initialization : more accurate handling of unknown variables #KT-13969 Fixed

(cherry picked from commit 4a96589)

compiler/testData/diagnostics/tests/controlFlowAnalysis/doWhileNotDefined.kt

@@ -0,0 +1,6 @@
+fun test(cond1: Boolean) {
+    do {
+        if (cond1) continue
+        val cond2 = false
+    } while (<!UNINITIALIZED_VARIABLE!>cond2<!>) // cond2 may be not defined here
+}

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

@@ -0,0 +1,3 @@
+package
+
+public fun test(/*0*/ cond1: kotlin.Boolean): kotlin.Unit

compiler/testData/diagnostics/tests/enum/localEnums.kt

@@ -5,7 +5,7 @@ fun foo() {
         FOO,
         BAR
     }
-    val foo = A.FOO
+    val foo = A.<!UNINITIALIZED_ENUM_ENTRY!>FOO<!>
     val b = object {
         <!WRONG_MODIFIER_TARGET!>enum<!> class B {}
     }