Consider adding terraform as an infrastructure-as-code option in addition to cdk

### Description

Our team primarily uses terraform to set up and manage cloudformation stacks. At the project creation step, you could expose an option to choose what IaC tool is desired. Currently cdk is the default and only method available. Maybe add a step where you could choose between terraform, cdk, serverless, sam and the others. I do see support for defining agentcore terraform modules [here](https://github.com/aws-ia/terraform-aws-agentcore). This feature can probably be based on that.

### Acceptance Criteria

- [ ] Add a step to choose the IaC before or after naming the project when running `agentcore create`.
- [ ] At the very least, users should be able to choose between cdk and terraform.

### Additional Context

_No response_

Start with the `agentcore create` flow and inspect how the current CDK choice is exposed during project creation. Review the linked terraform-aws-agentcore modules to understand the available Terraform support. Done means the command lets users choose at least CDK or Terraform and creates the selected IaC setup.

Written by the indexing model from the issue text.