[services][blob] Initial commit for Rust service

Summary:
This is my first project in Rust and I am new to the language,
so I wrote a classic hello-world app ;)

Initialized a fresh Rust project and set up generating code from proto.

Depends on D5675

Test Plan:

cd services/blob
cargo run

should build and display hello world

Reviewers: varun, jon, tomek, marcin

Reviewed By: varun, tomek

Subscribers: ashoat, atul

Differential Revision: https://phab.comm.dev/D5676