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

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

@@ -0,0 +1,12 @@
+enum class A { V }
+
+fun box(): String {
+    val a: A = A.V
+    when (a) {
+        A.V -> return "OK"
+    }
+}
+
+// 0 TABLESWITCH
+// 1 LOOKUPSWITCH
+// 1 ATHROW

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

@@ -0,0 +1,19 @@
+sealed class A {
+    object B : A()
+
+    class C : A()
+}
+
+fun box(): String {
+    val a: A = A.C()
+    val b: Boolean
+    when (a) {
+        A.B -> b = true
+        is A.C -> b = false
+    }
+    return if (!b) "OK" else "FAIL"
+}
+
+// 0 TABLESWITCH
+// 0 LOOKUPSWITCH
+// 1 ATHROW