[services][blob] Introduce HTTP server

Summary:
Final diff for ENG-3520.
This diff introduces a basic HTTP server with a hello world endpoint.

Also added CLI configuration option to switch between HTTP and GRPC servers. The default is gRPC to maintain backwards compatibility.

Depends on D7443

Test Plan:

• Service builds and starts gRPC server by default
• Running --protocol http starts HTTP server instead.
• The --port option works for both gRPC and HTTP servers.
• Calling GET /hello HTTP endpoint returns "Hello, World"

Reviewers: marcin, tomek, jon, varun, michal

Reviewed By: tomek

Subscribers: ashoat, atul

Differential Revision: https://phab.comm.dev/D7444