Add task to produce Docker context artifacts

[jasontedor]

Today we have tasks to produce Docker images which builds the default and OSS Docker images and publishes these to a local Docker registry. Additionally, we have a task that produces a Dockerfile and Docker context that can be used to build a Docker image from published release artifacts. This Dockerfile and Docker context is published to the elastic/dockerfiles repository after each release. We want to integrate the production and publication of these artifacts with our release process, and for this it means that we would add a task that bundles this Dockerfile and Docker build context into a compressed archive for consumption by the release process.

[elasticmachine]

Pinging @elastic/es-core-infra