lock_api not safe to use because inner maps use u64 hashes but DashMap only exposes `hash_usize`

[Diggsey]

I have a case where I need to look up a key, if it's there, return it, otherwise allocate a new item and return it. The key type I'm using for lookups doesn't match the key type of the map, so I cannot use the entry API. The raw-api doesn't expose the necessary functionality (hash_u64) and TBH it should just be using u64 hashes everywhere for consistency.