Demo: Add Terraform configuration files for stack migration and AWS provider setup

[sujaysamanta]

This pull request introduces a new Terraform stacks-based infrastructure setup, including configuration, component, and deployment files generated by tf-migrate, as well as supporting infrastructure for managing stack migration using the tfe and tfmigrate providers. The changes update the AWS provider version and add all necessary files for defining, deploying, and migrating Terraform stacks.

The most important changes are:

Terraform Stacks Infrastructure Setup:

• Added a set of generated files in _stacks_generated/ to define a reusable EC2 instance component (ec2_instance), its variables, outputs, provider configuration, and deployments for dev and prod workspaces. These files leverage the latest AWS provider and use variable sets for AWS credentials. [1] [2] [3] [4] [5] [6] [7]

Stack Migration Infrastructure:

• Introduced the stacks_migration_infra/ directory with Terraform configuration to manage stack migration using the tfe and tfmigrate providers. This includes resources for creating Terraform Cloud projects, stacks, and running migrations, as well as necessary variables and outputs. [1] [2] [3] [4]

Configuration and Version Management:

• Updated the root .terraform.lock.hcl to require AWS provider version 6.28.0 and adjusted constraints and hashes accordingly.
• Added a stack-migrate-config.hcl file to configure organization, project, stack, and workspace-to-deployment mappings for the migration process.

These changes lay the foundation for managing Terraform infrastructure using the new stacks model and automate the migration process to Terraform Cloud.