Add IAM user login profile

[dav3r]

🗣 Description

This PR adds IAM user login profiles in Terraform.

💭 Motivation and context

This change will eliminate the need to manually login to the AWS web console to enable a new user's console access and create their initial password. Those steps will now be handled automatically when this Terraform is applied.

Note that previously-created users must have their login profiles imported or else re-applying this Terraform will reset the console passwords of those users (see "Post-merge checklist" below).

🧪 Testing

I applied this Terraform in a fresh environment and confirmed that the users were all created along with their initial passwords. I also made sure that once a user changed their initial password, re-applying this Terraform did NOT reset their password.

I also tested the process of importing the user profile for previously created users and confirmed that it worked as expected with a command like this:

terraform import -var-file=my-env.tfvars aws_iam_user_login_profile.users[\"test.user\"] test.user

✅ 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

• terraform import IAM user profiles for users in all existing environments

[mcdonnnj]

LGTM ✔ I have one minor question for you.

[jsf9k]

I have one minor change request.