Generate `zilla dump` packet captures in timestamp order including across workers

[jfallows]

Describe the desired outcome from the user's perspective
As devops, I want to see zilla dump packet captures show packets in the order they occurred to more easily diagnose frames happening between packets across workers.

Acceptance criteria

• Merge sort the packets during generation such that packet number order and timestamp order are consistent
• No longer need to explicitly sort by timestamp in wireshark to see what is happening in order

Additional context
None