Consider using container image Lambdas for log ingestion

[schlarpc]

This allows everything to be version controlled, but also makes setup more of a pain.

Pros:

• runtime environment can be pinned/expressed in Nix flake
• no worrying about Lambda runtime deprecations

Cons:

• deployment is no longer a single JSON artifact
• need an ECR repository to bootstrap
• ECR storage costs money ($0.10/GB/mo after 50GB free tier)
• image synthesis / deployment tooling required (need to publish my existing skopeo-based tooling publicly)

Also, this only really makes sense to do after #3, as we can't use container image functions for Lambda@Edge.