Move Core Dockerfile into repo and reduce size

[leighmcculloch]

What

Move the Core Dockerfile used to build core into the repo, and reduce the image artifact by making its final step minimal.

Why

Reduce the size of intermediary images that are stored and passed around between jobs. It reduces the time copying images between jobs, and reduces the total size of artifacts stored in GitHub actions.

[anupsdf]

Reduce the size of intermediary images that are stored and passed around between jobs. It reduces the time copying images between jobs, and reduces the total size of artifacts stored in GitHub actions.

Can caching help here? Another idea is to explore if we can use the SDF internal docker registry to download the image instead of building it. Core's Jenkins job creates packages and puts them in docker-registry.services.stellar-ops.com/dev/stellar-core:23.0.2-2735.f5fba53aa.jammy...

[leighmcculloch]

Can caching help here? Another idea is to explore if we can use the SDF internal docker registry to download the image instead of building it. Core's Jenkins job creates packages and puts them in docker-registry.services.stellar-ops.com/dev/stellar-core:23.0.2-2735.f5fba53aa.jammy...

This repo already heavily use caching. This repo builds from source so we can produce quickstart images of any software components, which is why it doesn't download packages from other sources prebuilt.

[leighmcculloch]

For some reason this PR auto merged even though the build was failing. Investigating.