Add entry_refresh

[Yosi-Hezi]

• Add entry_refresh to enable entry API for LRU cache implementations (Combines get_refresh and entry implementations).
• Add tests for the entry_refresh:
  • Copies entry tests
  • Add new test to ensure using entry_refresh moves the entry to the end of the list

[Yosi-Hezi]

I know this project is in maintenance mode, but I think that this small addition is super useful and important, especially for LRU caching use cases.
For example: we can lru_cache.entry_refresh(key).or_insert_with(value) without the need to hash twice.

Let me know what you think and thank you for this great crate!