Decide on Style Guidelines for Terraform Code

# 💡 Summary #

We should have a style guide for Terraform (HCL) code just as we do for Python.

## Motivation and context ##

It's currently more just team lore as to what the preferences for how we write Terraform code. This include things like ordering statements, common permissions for common policies, and preferred naming. This will not only help the team write consistent Terraform code, but will also help in our collaboration with other developers who want to integrate with our Terraform-defined environments.

## Implementation notes ##

This should be a new `languages/terraform` or `languages/hcl` (that may cause confusion because Packer has started moving to HCL and would likely want its own style guide). It can just contain some core elements at first and will give us a go-to place to add information as we develop further guidelines internally.

## Acceptance criteria ##

- [ ] PR is created
- [ ] Everyone signs off on the PR