Generalize loading of shared folders

Summary:
This will auto-load any folder in the parent directory with the format "share-*"

It removes the prefix for the mount path. So for example, the parent directory should have "share-inbox-eas" to mount it at "/inbox-eas" within the VM

Test Plan: doesn't impact tests

Reviewers: kav-ya

Reviewed By: kav-ya

Differential Revision: https://review.inboxapp.com/D167