Method allocator

bolt/common/caching/AsyncDataCache.h:739–741

  uint64_t shrink(uint64_t targetBytes) override;

  memory::MemoryAllocator* allocator() const override {
    return allocator_;
  }

  /// Finds or creates a cache entry corresponding to 'key'. The entry
  /// is returned in 'pin'. If the entry is new, it is pinned in