Support Graviton portscan instances

[mcdonnnj]

🗣 Description

Add the ability spin up Graviton-based portscan instances in addition to x86_64 ones.

💭 Motivation and context

As part of our move to use Graviton-based instances (mainly for cost-benefits), and with the addition of ARM64-based AMIs added in #867, we can use portscan instances running on Graviton instances due to their straightforward configuration. Any Graviton-based instances will be deployed after any x86_64-based instances in sequence. Thus, with the configuration

nmap_instance_count = {
  arm64  = 1
  x86_64 = 1
}

portscan1 will be x86_64 and portscan2 will be ARM64. This method was chosen because it is of minimal impact to our existing configuration and helper scripts.

Warning

This is a breaking change because the format of the nmap_instance_count variable has changed from a number to an object where each key is an architecture and the value is the number of instances using that architecture.

🧪 Testing

Automated tests pass. I deployed Graviton-based portscan instances in my testing environment both in addition to x86_64 instances and exclusively. I verified that they received work and were able to process it successfully.

✅ 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.

[Copilot]

Pull Request Overview

This PR adds support for Graviton (ARM64) instances for the portscan service alongside existing x86_64 instances. This is a breaking change that modifies the nmap_instance_count variable from a simple number to an object specifying counts per architecture.

• Changed nmap_instance_count variable from number to object with arm64 and x86_64 keys
• Added separate AMI data sources for ARM64 and x86_64 architectures
• Updated instance provisioning to use appropriate AMI and instance type based on architecture
• Modified all count references to use the total calculated from both architectures

Reviewed Changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
terraform/variables.tf	Updates nmap_instance_count variable type and description
terraform/locals.tf	Adds calculation for total nmap instance count across architectures
terraform/cyhy_nmap_ec2.tf	Implements dual-architecture AMI selection and instance type logic
terraform/cyhy_nmap_cloud_init.tf	Updates cloud init count to use total instance count
terraform/cyhy_mongo_ec2.tf	Updates commander configuration to use total instance count
terraform/README.md	Updates documentation to reflect variable type changes

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[dav3r]

👍 👍

[mcdonnnj]

@cisagov/vm-dev I have updated the production tfvars file to align with the changes in this pull request (specifically the change to the nmap_instance_count variable).