FEAT: Test Runner - Add the rest of the testsuite run process + run CLI

[bentvelj]

Related: From https://github.com/aws/aws-sam-cli/pull/4065, I changed some file names and refactored the environment variable validation to the command entry point so that it fails faster in the case of invalid environment variables.

Which issue(s) does this change fix?

N/A

Why is this change necessary?

In order to actually run their integration tests, customers need a sam test-runner run command. The high level run process is as follows:

1. Deploy or update the Test Runner Stack
2. Upload customer tests and requirements to run those tests to an S3 bucket
3. Dispatch a runTask query to spin up a test-running Fargate container
4. Wait for the Fargate container to place results in the bucket, then download and print said results

How does it address the issue?

Includes the sam test-runner run command and the code for the run testsuite process

What side effects does this change have?

N/A

Mandatory Checklist

PRs will only be reviewed after checklist is complete

• [x] Add input/output type hints to new functions/methods
• [ ] Write design document if needed (Do I need to write a design document?)
• [x] Write/update unit tests
• [ ] Write/update integration tests
• [ ] Write/update functional tests if needed
• [x] make pr passes
• [ ] make update-reproducible-reqs if dependencies were changed
• [x] Write documentation

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.