[services][backup] Bootstrap new Rust project

Summary:
Created a standard cargo project structure. Linked proto code generation.

Adding @ashoat as creating a project introduces dependencies. These are almost 1:1 copy-pasted from blob service.

Depends on D5841

Test Plan: cargo run succeeds and prints hello world.

Reviewers: varun, ashoat, tomek, jon

Reviewed By: varun, ashoat, tomek

Subscribers: atul, ashoat

Differential Revision: https://phab.comm.dev/D5842