Switch to reusable workflow for building Docker image

[hturner]

1. Convert the Build and publish Docker image workflow to a reusable workflow. The workflow should build a container and add this container to a manifest file.
2. Create a second workflow that uses the reusable workflow from step 1 to build an amd64 container.

This should be equivalent to our current set-up, but we can then use the reusable workflow for building arm64 containers.