Rename SuccessOrFailure to Result and hide Failure from ABI

* The members of Result are isSuccess, isFailure, exceptionOrNull, getOrNull
* The rest of API is implemented via inline-only extensions
* There are two internal functions to hide detailed mechanics of an internal
  Result.Failure class: createFailure and throwOnFailure
* Result.toString is explicit: either Success(v) or Failure(x)

See KT-26538

compiler/testData/codegen/box/coroutines/debug/debuggerMetadata.kt

@@ -99,7 +99,7 @@ fun box(): String {
     if (res != "first") {
         return "" + res
     }
-    continuation!!.resumeWith(SuccessOrFailure.success(Unit))
+    continuation!!.resumeWith(Result.success(Unit))
     res = (continuation!! as BaseContinuationImpl).getSpilledVariableFieldMapping()!!.toMap()["I$0"] ?: "multipleLocalsInOneSlot fail 2"
     if (res != "second") {
         return "" + res

compiler/testData/codegen/box/coroutines/inlineClasses/bridgeGenerationCrossinline.kt

@@ -10,30 +10,30 @@ fun builder(c: suspend () -> Unit) {
 }
 
 @Suppress("UNSUPPORTED_FEATURE")
-inline class SuccessOrFailure<T>(val a: Any?) {
+inline class Result<T>(val a: Any?) {
     fun getOrThrow(): T = a as T
 }
 
-abstract class SuccessOrFailureReceiver<T> {
-    abstract suspend fun receive(result: SuccessOrFailure<T>)
+abstract class ResultReceiver<T> {
+    abstract suspend fun receive(result: Result<T>)
 }
 
-inline fun <T> SuccessOrFailureReceiver(crossinline f: (SuccessOrFailure<T>) -> Unit): SuccessOrFailureReceiver<T> =
-    object : SuccessOrFailureReceiver<T>() {
-        override suspend fun receive(result: SuccessOrFailure<T>) {
+inline fun <T> ResultReceiver(crossinline f: (Result<T>) -> Unit): ResultReceiver<T> =
+    object : ResultReceiver<T>() {
+        override suspend fun receive(result: Result<T>) {
             f(result)
         }
     }
 
 fun test() {
     var invoked = false
-    val receiver = SuccessOrFailureReceiver<String> { result ->
+    val receiver = ResultReceiver<String> { result ->
         val intResult = result.getOrThrow()
         invoked = true
     }
 
     builder  {
-        receiver.receive(SuccessOrFailure("42"))
+        receiver.receive(Result("42"))
     }
     if (!invoked) {
         throw RuntimeException("Fail")

compiler/testData/codegen/box/coroutines/inlineClasses/bridgeGenerationNonInline.kt

@@ -10,30 +10,30 @@ fun builder(c: suspend () -> Unit) {
 }
 
 @Suppress("UNSUPPORTED_FEATURE")
-inline class SuccessOrFailure<T>(val a: Any?) {
+inline class Result<T>(val a: Any?) {
     fun getOrThrow(): T = a as T
 }
 
-abstract class SuccessOrFailureReceiver<T> {
-    abstract suspend fun receive(result: SuccessOrFailure<T>)
+abstract class ResultReceiver<T> {
+    abstract suspend fun receive(result: Result<T>)
 }
 
-fun <T> SuccessOrFailureReceiver(f: (SuccessOrFailure<T>) -> Unit): SuccessOrFailureReceiver<T> =
-    object : SuccessOrFailureReceiver<T>() {
-        override suspend fun receive(result: SuccessOrFailure<T>) {
+fun <T> ResultReceiver(f: (Result<T>) -> Unit): ResultReceiver<T> =
+    object : ResultReceiver<T>() {
+        override suspend fun receive(result: Result<T>) {
             f(result)
         }
     }
 
 fun test() {
     var invoked = false
-    val receiver = SuccessOrFailureReceiver<Int> { result ->
+    val receiver = ResultReceiver<Int> { result ->
         val intResult = result.getOrThrow()
         invoked = true
     }
 
     builder {
-        receiver.receive(SuccessOrFailure(42))
+        receiver.receive(Result(42))
     }
     if (!invoked) {
         throw RuntimeException("Fail")

compiler/testData/codegen/box/coroutines/reflect/callSuspend.kt

@@ -30,7 +30,7 @@ var proceed = {}
 
 suspend fun suspendHere() = suspendCoroutineUninterceptedOrReturn<Unit> { cont ->
     proceed = {
-        cont.resumeWith(SuccessOrFailure.success(Unit))
+        cont.resumeWith(Result.success(Unit))
     }
     COROUTINE_SUSPENDED
 }

compiler/testData/codegen/box/coroutines/reflect/callSuspendBy.kt

@@ -32,7 +32,7 @@ var proceed = {}
 
 suspend fun suspendHere() = suspendCoroutineUninterceptedOrReturn<Unit> { cont ->
     proceed = {
-        cont.resumeWith(SuccessOrFailure.success(Unit))
+        cont.resumeWith(Result.success(Unit))
     }
     COROUTINE_SUSPENDED
 }