CNG: Add container size output to end of jobs
Summary
Related https://gitlab.com/charts/gitlab/issues/1257
We should add an container image size report to the end of the various build jobs, so that we have visibility into the resulting outputs we're calling a final product, without the manual step of pulling them all.
Possibly, as a further extension, we can take this information to process expectations and issue warnings when the images are over a given size on a per-component basis.