Replace "in_file" helper method

What does this MR do and why?

Remove helper function in_file and replace it with is_subdir that utilizes a different module that better handles windows pathing.

The module used in in_file throws an exception when path letters are not the same. This causes problems whenever a user has a server or backup dir in a different drive letter than that of which Crafty is installed on.

How to set up and validate locally

Put backup directory on separate path letter Create a backup. Attempt to delete a backup.

MR acceptance checklist

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• Have you checked this doesn't interfere/conflict/duplicate someone elses work?
• Have you fully tested your changes?
• Have you resolved any lint issues?
• Have you assigned a reviewer?
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