dwarflint: Drop checkdescriptor::{prereq,inherit}

dwarflint: Drop checkdescriptor::{prereq,inherit}

- ... which was just duplicating the lint.check<> calls in check
  initializers.  It was needed for --list-checks to display all the
  checks.  Now we register all the checks that we either want to show
  in the list or run, and mark them as hidden or unscheduled as needed.
  We lose the ability to list dependees in --list-checks, but I don't
  think that is too interesting anyway.