…timezone via UUID

When the API call fails, added a new BukkitRunnable that will be scheduled to run after the retryDelay. It will retry adding the timezone to the map after the delay instead of adding it immediately. This way, we prevent overloading the API

getTimeZone now uses a new thread instead of a BukkitRunnable to handle the API request

Integrated 'ConcurrentHashMap' in place of 'Hashmap' to ensure the expansion is thread-safe
retryDelay was also migrated to a new 'getTimeZoneFromAPI' method, and appropriately initialized

I really need to sleep...

Implement cache expiration in DateManager
Optimize cache structure in DateManager
Return CompletableFuture in DateManager's getTimeZone
Adapt LocalTimeExpansion to work with updated DateManager

…e efficiency

Remove cache expiry checks from getTimeZone method
Remove data removal from onLeave event handler
Create a new scheduled task removeExpiredEntries to handle cache expiry and player data removal
Update isCacheExpired method to remove players from the timezones map when cache expires
Add a check in removeExpiredEntries to skip non-UUID keys in the cache
Remove unnecessary onLeave event handler and Listener implementation

`Shutdown` method to shut down the executor service on `clear()`
Fixed `getTimeZone` method to be non-blocking
Removed premature return of `CompletableFuture`