[cctest] Move most heap related tests to test/cctest/heap and clean wrt IWYU

test/cctest/test-slots-buffer.cc

 // Copyright 2015 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.
 
 // TODO(mythria): Remove this define after this flag is turned on globally
 #define V8_IMMINENT_DEPRECATION_WARNINGS
 
 #include "src/heap/slots-buffer.h"
 #include "test/cctest/cctest.h"
+#include "test/cctest/heap/utils-inl.h"
 
 namespace v8 {
 namespace internal {
 
 TEST(SlotsBufferObjectSlotsRemoval) {
   CcTest::InitializeVM();
   v8::HandleScope scope(CcTest::isolate());
   Isolate* isolate = CcTest::i_isolate();
   Heap* heap = isolate->heap();
   Factory* factory = isolate->factory();
@@ skipping 106 matching lines @@
   mark_bit = Marking::MarkBitFrom(*new_space_object);
   Marking::MarkWhite(mark_bit);
   mark_bit = Marking::MarkBitFrom(*old_space_object_non_evacuation);
   Marking::MarkWhite(mark_bit);
 
   delete buffer;
 }
 
 }  // namespace internal
 }  // namespace v8