(DRAFT) Push infra within agent package(s)

[athewsey]

Issue #, if available: N/A

Rationale:

As we think about expanding the sample towards a more "platform"y approach, I suggest to aim for a monorepo-like structure in which 1/ having multiple agents would make sense, and 2/ individual packages/projects are clearly self-contained.

Since it seems like terraform-provider-aws are gearing up towards launching resources for AgentCore including runtime (presumably after the service goes GA), I also wanted to explore how much of the agent ECR+deployment we could already support from Terraform side.

Description of changes:

This PR proposes to:

1. Move infra for the cx agent under its cx-agent-backend project folder, instead of the central /infra folder for the shared platform
2. Push the container build & deployment to ECR within the Terraform deploy process itself via local script provider pattern and the terraform_data resource
   • AFAIK build+deploying images within Terraform is not universally popular - some would argue (e.g. here) that tooling for it should be separated
   • ...But assuming we'd like to deploy downstream infrastructure like the Agent Runtime via TF later, we'd need to implement a proper pipeline to handle the multiple steps - ideally CICD-ified. Until we have something more extensive in place, smushing it into one Terraform deploy seemed like a nice way to keep the solution technologically consistent and faster to set up 🤷‍♂️

👷 It's currently incomplete:

• Only working with finch at the moment, not figured out how to smartly toggle between finch & docker yet
• I started towards bringing IAM role infra into the agent project itself, but didn't actually delete it from the main project yet so at the moment it's just duplicating
• Haven't updated deployment docs or notebook

...But putting out there to get some initial feedback and understand if folks are on board with the general direction

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