build: optimize apt-get cleanup during image build

[becker-s]

What type of PR is this?

• cleanup
• feature

What this PR does / why we need it:

This PR optimizes the Dockerfile steps that install packages via apt-get by modifying and adding apt-get cleanup steps:

• follow Docker best practices for apt-get cleanup: https://docs.docker.com/develop/develop-images/dockerfile_best-practices/#apt-get
• remove an obsolete and non-functional RUN that did not reduce the image size (the "cleaned up" data was persisted in previous image layers)
• remove apt autoremove as no packages are uninstalled

Which issue(s) this PR fixes:

None

Testing

You can build a new image with and without the PR changes and compare their size.
For the latest commit, the optimized production image was 18M smaller.

Release Notes

build: optimize apt-get cleanup during image build