[native] enable backup handler for staff
Summary:
Part of ENG-9604 but only for staff.
Starting Rust thread responsible for uploading Backup. Right now it will be used to upload User Keys only, but in the future, it will be used for User Data and logs.
Adding an alert to log if anything went wrong.
Test Plan: Add additional log to make sure if this is started or not, test it with iOS and Android (background/foreground/background).
Reviewers: bartek, tomek
Reviewed By: bartek
Subscribers: ashoat
Differential Revision: https://phab.comm.dev/D14056