[services] Backup - Add Rust

Summary:
Depends on D4860

Adding basic rust to the backup service.

Test Plan:
Backup service builds.

To use rust functions in the c++ code:

#include "rust_lib/src/lib.rs.h"

test_function();

Reviewers: tomek, varun, max, inka, ashoat

Reviewed By: tomek, varun, max, ashoat

Subscribers: jon, ashoat, tomek, adrian, atul, abosh

Differential Revision: https://phab.comm.dev/D4861