Update on the reencoding function

[Toyem]

Change the following points:

• Add a restore of previous files in case of failure during re-encoding
• Fix the "giving up issue" of files due to the deletion of the artwork on pixiv
• Fix rglob issue of re-encoding where files could be skipped for no apparent reason
• Implement the overwrite behavior into the re-encoding
• Implement the backupOldFile behavior where artwork rename by the author or the author renaming itself can cause the re-download of the artwork and left the previous one without proper re-encoding (so it's backup and save with a backup name)