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
Actually you can just use $@ directly.

And declare the loop variable (target) as local to prevent leaking it into the environment:

```
kube::binaries_from_targets() {
  local target
  for target; do
    echo "${KUBE_GO_PACKAGE}/${target}"
  done
}
```

(The `for` without any `in` defaults to looping over `"$@"` which is exactly what you want.)