message: Add a lock for loading the cache of frequently-used types
  Summary: Don't misuse the s_field_lock.
diff: @@ -161,9 +161,9 @@ struct RedexContext {
  m_pointers_cache_loaded = true;
  }
  const FrequentlyUsedPointers& pointers_cache() {
  - std::lock_guard<std::mutex> lock(s_field_lock);
  if (!m_pointers_cache_loaded) {
  redex_assert(!kDebugPointersCacheLoad);
  + std::lock_guard<std::mutex> lock(m_pointers_cache_lock);
  load_pointers_cache();
  }
  return m_pointers_cache;
  @@ -334,6 +334,7 @@ struct RedexContext {
  bool m_allow_class_duplicates;
  bool m_pointers_cache_loaded{false};
  + std::mutex m_pointers_cache_lock;
  FrequentlyUsedPointers m_pointers_cache;
  // Field values map specified by Proguard assume value
  