[commtest] Add dockerfile and entrypoint script

Summary:

• Created a bash script that initializes the localstack for tests, and then runs commtest integration tests. This script is the main entrypoint for the docker container that runs the tests on CI.
• Created a Dockerfile for commtest that install necessary dependencies and copies necessary files

Depends on D9510

Test Plan: Tested together with the next diff. It can work without it but setting up the environment manually is too cumbersome.

Reviewers: varun, michal, kamil, jon

Reviewed By: michal, kamil

Subscribers: ashoat, tomek, wyilio

Differential Revision: https://phab.comm.dev/D9511