Initial functionality

[dav3r]

🗣 Description

This PR contains the first version of Terraform code to perform the initial configuration of a newly-created COOL Cyber Hygiene (CyHy) AWS account.

💭 Motivation and context

This is a necessary first step towards having a CyHy account that is a full-fledged member of the COOL.

NOTE: Per team consensus, I will rename this repo from cool-accounts-cyhy to cool-accounts-cyhy-tf-root after this PR is merged.

🧪 Testing

I applied this Terraform in a development environment and verified that it worked as intended.

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• All relevant type-of-change labels have been added.
• I have read the CONTRIBUTING document.
• These code changes follow cisagov code standards.
• All relevant repo and/or project documentation has been updated
  to reflect the changes in this PR.
• All new and existing tests pass.

✅ Post-merge checklist

• Rename this repo from cool-accounts-cyhy to cool-accounts-cyhy-tf-root

[jsf9k]

• I think this account should also have the "disable inactive IAM users" jazz that I recently added to the COOL.
• Don't forget that when you rename you will have to migrate the state (defined in backend.tf) over to the new key name.

[dav3r]

• I think this account should also have the "disable inactive IAM users" jazz that I recently added to the COOL.

This was done in the following commits:

• 5eda35d
• 69a9de1
• 656be7c
• 949439d
• 8b3b6f2

[felddy]

Looks good. _{(I actually read it all.)}
Strong work! 💪

[felddy]

Even stronger! 🦾

[mcdonnnj]

Solid groundwork here 💪💪💪 Just a few questions for your consideration.

[jsf9k]

You need to remove the unused variables from the README.md as well.