fix awscli patch for new create_nested_client, introduce bats tests

[alexrashed]

Motivation

awscli version 1.41.9 comes with aws/aws-cli#9602, which changes the way the AWS client is created. This conflicts with our patch for Cloudformation (modifying the S3 endpoint URL).
This PR fixes this, and also introduces a proper testing framework (bats).
Fixes #91.

Changes

• Introduces a new test pipeline which runs certain smoke tests using bats.
• Fixes the patch of the create_client function for awslocal cloudformation package and awslocal cloudformation deploy.
  • Instead of using a fixed position in the outer frames, we now backtrack to see if we can find the right frame in the whole set of frames. This approach is compatible with the versions before 1.41.9, as well as the versions since then.

[github-actions]

Smoke Tests

 6 files  12 suites   3m 22s ⏱️
 4 tests  4 ✅ 0 💤 0 ❌
24 runs  24 ✅ 0 💤 0 ❌

Results for commit e066dce.

♻️ This comment has been updated with latest results.

[dominikschubert]

Thanks for jumping on this. I hope we can continue reducing our dependency on awslocal in the future but that's a great patch for now 👍

Appreciate the evolution of the CI workflow and you extending the test matrix to make sure we cover a version before the boundary version of this specific issue 🙏