Introduce a BuiltinsConstructStub that sets up new.target and does a [[call]] per ES6 9.3.2

src/api.cc

 // Copyright 2012 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.
 
 #include "src/api.h"
 
 #include <string.h>  // For memcpy, strlen.
 #ifdef V8_USE_ADDRESS_SANITIZER
 #include <sanitizer/asan_interface.h>
 #endif  // V8_USE_ADDRESS_SANITIZER
@@ skipping 6106 matching lines @@
   DCHECK(num_flags <= static_cast<int>(arraysize(flags_buf)));
   return isolate->factory()->InternalizeOneByteString(
       i::Vector<const uint8_t>(flags_buf, num_flags));
 }
 
 
 MaybeLocal<v8::RegExp> v8::RegExp::New(Local<Context> context,
                                        Local<String> pattern, Flags flags) {
   PREPARE_FOR_EXECUTION(context, "RegExp::New", RegExp);
   Local<v8::RegExp> result;
-  has_pending_exception =
-      !ToLocal<RegExp>(i::Execution::NewJSRegExp(Utils::OpenHandle(*pattern),
-                                                 RegExpFlagsToString(flags)),
-                       &result);
+  has_pending_exception = !ToLocal<RegExp>(
+      i::JSRegExp::New(Utils::OpenHandle(*pattern), RegExpFlagsToString(flags)),
+      &result);
   RETURN_ON_FAILED_EXECUTION(RegExp);
   RETURN_ESCAPED(result);
 }
 
 
 Local<v8::RegExp> v8::RegExp::New(Local<String> pattern, Flags flags) {
   auto isolate =
       reinterpret_cast<Isolate*>(Utils::OpenHandle(*pattern)->GetIsolate());
   auto context = isolate->GetCurrentContext();
   RETURN_TO_LOCAL_UNCHECKED(New(context, pattern, flags), RegExp);
@@ skipping 2387 matching lines @@
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   callback(info);
 }
 
 
 }  // namespace internal
 }  // namespace v8