Problem/Motivation
Spun off from #3087644: Remove Drupal 8 updates up to and including 88** where we identified that trying to remove all updates in one go resulted in an enormous patch that was too difficult to review.
Proposed resolution
As per #79 from that issue, we can try and remove update hooks and tests from system.module on their own.
Remaining tasks
Figure out what else is needed for patch to pass.