Run now takes a context as well as a statebag. We'll assign the context
to the blank identifier to prevent namespace collisions. We'll let the
step authors opt-in to using the context.
`find . -iname "step_*.go" -exec gsed -i'' 's/func \(.*\)Run(/func \1Run(_ context.Context, /' {} \;`
This adds support for authenticating towards ECR in the docker builder
and docker-push post-processor using them same mechanisms as in the
amazon builders. I.g. access key/secret key, credentials on file,
environment variables, sts tokens or IAM instance roles.