Reduce CI go module downloads, add make targets (#18708, #18475, #18443…

…) (#18741)

Backport #18708 
Backport #18475 
Backport #18443 

The CI currently downloads all go modules in each pipeline step because go modules reside outside the project directory. Fix this by introducing a volume for the `/go` directory [1] so modules are only downloaded once per pipeline using a new `deps-backend` make target.

For completeness, I also included new `deps` and `deps-frontend` targets and the frontend one is also triggered explicitly on CI where needed.

[1] https://docs.drone.io/pipeline/kubernetes/examples/language/golang/#dependencies

* Also backports #18475 and #18443 so that is was able to merge cleanly.
Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>