Turn import ordering violations into build errors, plus a few adjustments
to account for how the checker behaves. I'm a little on the fence about
whether the existing code is right, but it's easier to appease the checker
than to discuss what's the more correct order here.

Plus a few fixes to imports that cropped in since my recent cleanups.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #10612 from vanzin/SPARK-3873-enable.