[services][feature-flags] Introduce AWS config

Summary:
Add new configuration for AWS and localstack. Versions of added libraries are the same as in backup service.
Depends on D6666

Test Plan: Write additional code to connect to dynamodb instance and check if it is possible to list all the tables both from remote and localstack instance.

Reviewers: michal, bartek, jon, varun

Reviewed By: bartek, varun

Subscribers: ashoat, atul

Differential Revision: https://phab.comm.dev/D6687