Rework the scheduler and file utility

[GiantTreeLP]

The scheduler is very weird and wastes resources. The TaskScheduler is very weirdly set up and requires major rewriting.

This is very noticable with long lasting tasks like copying a large template.

https://github.com/CloudNetService/CloudNet/blob/development/cloudnet-lib/src/main/java/de/dytanic/cloudnet/lib/utility/threading/Scheduler.java

https://github.com/CloudNetService/CloudNet/blob/development/cloudnet-lib/src/main/java/de/dytanic/cloudnet/lib/scheduler/TaskScheduler.java

It would be best to simply replace this large class with a ScheduledExecutorService

While we are at it, we should also rewrite the FileUtility to use ready-made methods directly from Java: https://github.com/CloudNetService/CloudNet/blob/development/cloudnet-wrapper/src/main/java/de/dytanic/cloudnetwrapper/util/FileUtility.java.

Current progress:

• [x] FileUtility
• [x] TaskScheduler

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