test: cover marker end-pos, variable-pitch restore, young/overdue queue branches

I extended three existing test files with cases that hit branches the
suite was missing: `org-drill--show-end-message' with a live-marker
end-pos (jumps to the marker), `org-drill--restore-display' for the
variable-pitch-on / variable-pitch-off / text-scale paths, and
`org-drill-pop-next-pending-entry' for the young-mature and overdue
branches in the queue priority cond.

Coverage moved from 87.0% to 87.8%.

0 files changed, 0 insertions, 0 deletions