Refactor the installation of the environment secrets

Prior to this commit, this installed the secrets using multiple functions roughly doing the same thing. This clarifies the deployment by using no indirection and directly call one function (which installs as before the secrets).

The review must be done commits per commits. Each commit does its best to only modify one deployment. The last commit dropping the no longer used functions.

All tests were executed one commit by commit (sandboxed) with minikube (which now defines secrets [in this very diff too] to ensure no surprises will rise when actually deploying this in real clusters).

Note:

• That allowed me to see an issue with the loader-deposit part (which got cherry-picked from this mr). So it's fixed.
• The initial commits turns the minkube swh services off by default (which had been activated by mistake at some point by me).