Revert changes to batch the insertion of pages into page queues.

It will be replaced by a more general mechanism in a future commit.
The approach in this change has a number of disadvantages:

• It bloats the per-domain structure quite a bit: we keep a batch queue per page lock per page queue, for a total of PQ_COUNT*PA_LOCK_COUNT queues per domain. We'd like to be able to increase PA_LOCK_COUNT without incurring bloat.
• It only improves scalability for enqueue operations; threads which wish to dequeue or requeue pages still must acquire the page queue lock. Thus, the page queue lock remains a bottleneck in certain workloads. Builds, for example, involve frequent removal of pages from PQ_ACTIVE as short-lived VM objects are destroyed.
• The page daemon still needs to acquire the page queue lock once per page during a queue scan.