[builtins] Move more files into v8_builtins_generators source set

src/builtins/builtins-async.h

-// Copyright 2016 the V8 project authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef V8_BUILTINS_BUILTINS_ASYNC_H_
-#define V8_BUILTINS_BUILTINS_ASYNC_H_
-
-#include "src/builtins/builtins-promise.h"
-
-namespace v8 {
-namespace internal {
-
-class AsyncBuiltinsAssembler : public PromiseBuiltinsAssembler {
- public:
-  explicit AsyncBuiltinsAssembler(compiler::CodeAssemblerState* state)
-      : PromiseBuiltinsAssembler(state) {}
-
- protected:
-  typedef std::function<Node*(Node*)> NodeGenerator1;
-
-  // Perform steps to resume generator after `value` is resolved.
-  // `on_reject_context_index` is an index into the Native Context, which should
-  // point to a SharedFunctioninfo instance used to create the closure. The
-  // value following the reject index should be a similar value for the resolve
-  // closure. Returns the Promise-wrapped `value`.
-  Node* Await(Node* context, Node* generator, Node* value, Node* outer_promise,
-              const NodeGenerator1& create_closure_context,
-              int on_resolve_context_index, int on_reject_context_index,
-              bool is_predicted_as_caught);
-};
-
-}  // namespace internal
-}  // namespace v8
-
-#endif  // V8_BUILTINS_BUILTINS_ASYNC_H_