CFG exhaustive when else instruction for KT-8700

compiler/testData/diagnostics/tests/when/ExhaustiveBreakContinue.kt

@@ -0,0 +1,14 @@
+enum class Color { RED, GREEN, BLUE }
+
+fun foo(arr: Array<Color>): Color {
+    loop@ for (color in arr) {
+        when (color) {
+            Color.RED -> return color
+            Color.GREEN -> break@loop
+            Color.BLUE -> if (arr.size == 1) return color else continue@loop
+        }
+        // Unreachable
+        <!UNREACHABLE_CODE!>return Color.BLUE<!>
+    }
+    return Color.GREEN
+}