Add reachability E2E test using Terratest

[dragonfleas]

Implement the following tests:

End to End tests verifying that the ECS service can deploy and run using a nginx web server and is reachable with a public IP
Check block assertion that returns an error if the task definition provided cannot be used/isn't parsable

[dragonfleas]

I think we are going to pivot and upgrade the modules to use Terraform 1.7.X and use native testing functionality first. If we encounter any big restrictions or need to just use terratest to integration testing or smoke tests we will do that.

[dragonfleas]

Closing as we're going to opt to keep using Terratest until something promising comes from OpenTofu or Hashicorp, right now the current testing implementation sucks.

[dragonfleas]

On second thought, I'm going to re-purpose this issue so we can track our findings of ☝🏼 (that being terraform's native testing suite not being great)