[client] display: use trusted nominal cadence

Always track Wayland surface outputs alongside fractional scaling and use
RandR modes for X11 cadence. Remove render-derived feedback so a
throttled client cannot teach the producer to remain throttled.

Release scheduling after nominal output timing remains unavailable.

client/displayservers/Wayland/presentation.c

@@ -76,15 +76,7 @@ bool waylandGetFramePeriod(uint64_t * period)
   /* Frame demand must use the output's nominal rate. Basing demand on the
    * observed presentation interval can lock a VRR session at its current,
    * slower cadence. */
-  if (waylandOutputGetFramePeriod(period))
-    return true;
-
-  const uint64_t value = atomic_load(&wlWm.presentationPeriod);
-  if (!value)
-    return false;
-
-  *period = value;
-  return true;
+  return waylandOutputGetFramePeriod(period);
 }
 
 static void presentationFeedbackDiscarded(void * data,