Standardize FROM statement format in Dockerfiles

Currently, the FROM statements in Dockerfiles are formatted like this:

ARG BASE_REGISTRY=nexus-docker-secure.levelup-nexus.svc.cluster.local:18082
ARG BASE_IMAGE=gitlab/gitlab/gitlab-ruby
ARG BASE_TAG=15.2.1

ARG RUBY_IMAGE=${BASE_REGISTRY}/${BASE_IMAGE}:${BASE_TAG}

FROM ${RUBY_IMAGE}

For DSOP releases, repo1 linter doesn't like the use of the RUBY_IMAGE variable so we received a request to modify the release helper script to make all FROM statements look like this for all containers:

FROM ${BASE_REGISTRY}/${BASE_IMAGE}:${BASE_TAG}

Doing this has the added side benefit of simplifying the code in the Release Helper script because the same script function can be used for all containers when releasing GitLab to DSOP