Refactor DynamicBackup, accompanying bug fixes

[NickBonet]

• When using dynamic backup, Nether & End region files weren't properly backed up by ZipManager, this was also patched.
• Simplified backupInfo.yml, doesn't seem like the World objects needed to be serialized to YAML, instead just serialized a few details so that the YAML paths for regions were still written as expected. Fixes global tag issues when loading backupInfo.yml next server boot.
• Removed the internal chunks array from DynamicBackup and refactored the class to utilize DRY principles.
  • At times, the way the chunks array was accessed was causing out of bounds exceptions.
  • In addition, after reviewing the logic, it didn't seem necessary to keep an internal array as its state could get messy over time, depending how events/tasks were handled.
• Moved saveChanges() to ServerBackup, allowing it to be used everywhere saveBpInf() was being used prior.
• Added try-with-resources block to Files.walk() usage in ZipManager