Review apps: add Terraform in support of forms-runner review apps

[AP-Hunt]

What problem does this pull request solve?

Trello card: https://trello.com/c/4r1IFARH/675-add-review-apps-to-forms-runner

This Terraform is cloned from the equivalent code in forms-admin, and adjusted for the needs of forms-runner. The code duplication is a choice we made, because these two sets of Terraform code are only similar, and not the same bar some parameter differences. Trying to share code between the two would cause more problems than it solves.

Things to consider when reviewing

• Ensure that you consider the wider context.
• Does it work when run on your machine?
• Is it clear what the code is doing?
• Do the commit messages explain why the changes were made?
• Are there all the unit tests needed?
• Do the end to end tests need updating before these changes will pass?
• Has all relevant documentation been updated?

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[sarahseewhy]

This looks solid. There's nothing that I can see which needs changing. Code is clear and I appreciate all the comments and documentation. Thank you 🪄

[github-actions]

🎉 A review copy of this PR has been deployed! It is made of up two components

1. A review copy of forms-runner
2. A production copy of forms-admin

Important

Not all of the functionality of forms-runner is present in review apps.
Functionality such as sending emails, file upload, and S3 submission types are
deliberately disabled for the sake of simplifying review apps.

You should use the full dev environment to test the functionality which is disabled here.

It may take 5 minutes or so for the application to be fully deployed and working. If it still isn't ready
after 5 minutes, there may be something wrong with the ECS task. You will need to go to the integration AWS account
to debug, or otherwise ask an infrastructure person.

For the sign in details and more information, see the review apps wiki page.