NewShardedLRUCache creates a ShardedLRUCache.

NewSimpleLRUCache creates a SimpleLRUCache object, whose capacity is "capacity".

ShardedLRUCache is a sharded LRU Cache, thread safe.

SimpleLRUCache is a simple least recently used cache, not thread-safe, use it carefully.

Key is the interface that every key in LRU Cache should implement.

Value is the interface that every value in LRU Cache should implement.