Implicit exhaustive whens now have exception in else branch #KT-8700 Fixed

compiler/testData/codegen/bytecodeText/when/exhaustiveWhenInitialization.kt

@@ -0,0 +1,14 @@
+enum class A { V }
+
+fun box(): String {
+  val a: A = A.V
+  val b: Boolean
+  when (a) {
+    A.V -> b = true
+  }
+  return if (b) "OK" else "FAIL"
+}
+
+// 0 TABLESWITCH
+// 1 LOOKUPSWITCH
+// 1 ATHROW