Build speed: Install/installer:docker

[mads-hartmann]

Builds of install/installer:docker is taking rather long (40s) even when the component source code isn't changed.

Looking at the Dockerfile we see that the order commands can be improved with respect to layer caching. We should move line 9 just below COPY --from=alpine/helm:3.8.0 /usr/bin/helm /usr/bin/helm

[mads-hartmann]

Reopening as PR was reverted in #12860