Over a year ago, it was mentioned that keeping this code around until we could fix up the block priority stuff might be useful. It's clear that the cost of maintaining this code is not worth keeping it around, so I'm happy to see this go. Maybe one day we can revisit the concept.

Reviewer note: This is similar in many ways to PR9602 which removes -blockprioritysize which was the original name of the argument before it was changed to -blockprioritypercentage in D485.