[services] Tests - Add performance tests base for Blob

Summary:
Depends on D4580

This is the base code for the performance tests for the Blob service.

I used tokio here as I was having problems with thread::spawn thread::join working with the async closures - @varun have you done anything like this? I'm not saying that tokio's bad here - there's some additional boilerplate but not too much - acceptable I'd say.

The idea here is to simultaneously run service calls (they're async) in multiple threads.

Test Plan:

cd services
yarn run-performance-tests blob

It doesn't do anything with the service yet but should compile and pass.

Reviewers: tomek, varun, ashoat

Reviewed By: tomek, ashoat

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

Differential Revision: https://phab.comm.dev/D4581