Auto deploy gitlab-workhorse, gitaly, and gitlab-shell
This is the next step after !716 (merged)
This MR enables auto deploy of gitlab-workhorse, gitaly, and gitlab-shell
Because not all the components have the same level of code coverage in end-to-end testing, I introduced a feature flag for each one.
We could merge this as-is, and enable only components we trust to have proper testing in place.
Edited by Alessio Caiazza