Move targets and packages from build-go to config-go

@filbranden This should help with building things not using the build-go script and doing it by hand.  This should be the last of the 'brains' in build-go.sh
In fact, here as well you could echo one target per line instead of words on the same line.

For someone using `targets=$(kube::default_build_targets)` that doesn't make a difference but it's cleaner if you want to use other constructs (e.g. `| while read target; do ...`).