Bootstrap AWS infrastructure

[ships]

Status: WIP.

Issue(s) Resolved

This PR introduces Terraform and Github Actions as declarative infrastructure and change management stack.

Test Plan

Screenshots (if applicable)

Optional

Notes/Context/Gotchas

TODOS:

• document test plan
• Enable separation of deploy step from build step entirely. By checking for existence of container image?
• Build image for all packages at once, and only distinguish them at runtime?
• Introduce all needed env vars to the Terraform
• Document use of .tfvars and .tfbackend

Supporting Docs

[kalilsn]

Sorry for the slow review. This looks like a great base to build on, and I think you captured all my feedback in your TODOs anyways. Since these are all additive changes (with the exception of the permission fix on our build script), I think it's fine to address those in future PRs