实现个 Buffer Pool(Extendible Hasing/LRUK Replacer)

  /**
   *
   * TODO(P1): Add implementation
   *
   * @brief Insert the given key-value pair into the hash table.
   * If a key already exists, the value should be updated.
   * If the bucket is full and can't be inserted, do the following steps before retrying:
   *    1. If the local depth of the bucket is equal to the global depth,
   *        increment the global depth and double the size of the directory.
   *    2. Increment the local depth of the bucket.
   *    3. Split the bucket and redistribute directory pointers & the kv pairs in the bucket.
   *
   * @param key The key to be inserted.
   * @param value The value to be inserted.
   */
  void Insert(const K &key, const V &value) override;