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

ProfileName is the function name in heap profile.

GlobalLRUMemUsageTracker tracks all the memory usage of SimpleLRUCache.

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.