Investigate how to extract EE-specific files/lines of code for JavaScript, CSS, Grape API, Routes, Config/initializers

In this issue, we should discuss and investigate how we can extract EE-specific lines of code from:

• JavaScript
• CSS
• Grape API
• Views
• Routes
• Config/initializers
• Test factories
• YAML files?

Related to:

• &27 (closed)
• https://gitlab.com/gitlab-org/gitlab-ee/issues/3107
• gitlab-com/www-gitlab-com!9486 (merged)
• https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/17573