* Use Rc to prevent clone of Packets
* Fix min => max in banking_stage threads.
Coalesce packet buffers better since a larger batch will
be faster through banking and sigverify.
Deconstruct batches into banking_stage from sigverify since
sigverify likes to accumulate batches but then a single banking_stage
thread will be stuck with a large batch. Maximize parallelism by
creating more chunks of work for banking_stage.