pack: exempt votes and bundles from pacing, schedule votes first

[ptaffet-jump]

The policy is now:

Bank 0 when pacing says it should be inactive (the first X ms of the block):

1. If there's a vote, schedule it and return.
2. If there's a bundle (almost certainly schedulable), schedule it and return.

Bank 0 when pacing says it should be active (the rest of the block):

1. If there's a vote, schedule it and return.
2. If there's a bundle that can be scheduled, schedule it and return.
3. If there weren't any bundles, or the next one doesn't fit in the rest of the block, try to schedule a normal transaction
   Note: if there was a bundle but it couldn't be scheduled because of account conflicts, don't schedule anything.

Bank >0 when pacing says it should be inactive:

1. If there's a vote, schedule it and return

Bank >0 when pacing says it should be active:

1. If there's a vote, schedule it and return
2. Try to schedule a normal transaction