deploy Terraform modules without wrapping scripts

[glennmusa]

Description

This change removes the BASH scripts from src/scripts and updates the Terraform modules to deploy from the command-line with native Terraform CLI commands without any modifications to source.

There are extensive docs updates to this changeset, so please do tear my grammar and instructions apart where necessary!

To demo this, follow the instructions at src/terraform/README.md:

1. Deploy the root module at src/terraform/mlz/main.tf with just terraform apply
2. Make note of the outputs so that you can...
3. Deploy the new workload module at src/terraform/tier3/main.tf with just terraform apply
4. Clean up the new workload module at src/terraform/tier3/main.tf with just terraform destroy
5. Clean up the root module at src/terraform/mlz/main.tf with just terraform destroy

Issue reference

The issue this PR closes #409

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles or validates correctly
• All tests pass (manual and automated)
• The documentation is updated to cover any new or changed features
• Markdown files have been linted using the recommended linter. (See .vscode/extensions.json.)
• Relevant issues are linked to this PR