add support for integration test via GitHub Actions

[maxday]

✍️ Description of changes:

This PR enable automatic integration testing via GitHub Actions.
This will create and destroy new stacks on each run.
Integration tests are also written in Rust and run via idiomatic cargo run
For now, tests are really simple : hello world + asserting that the status code is 200 but this PR is building the fondations for more complex testing.

I've check that the action is actually running correclty:

🔏 By submitting this pull request

• I confirm that I've ran cargo +nightly fmt.
• I confirm that I've ran cargo clippy --fix.
• I confirm that I've made a best effort attempt to update all relevant documentation.
• I confirm that my contribution is made under the terms of the Apache 2.0 license.

[calavera]

Awesome!