Pcapusendqueue_transmit_npf has a large packet interval delay

[liuzhongzhu]

Pcapusendqueue_transmit_npf adopts asynchronous mode. When sending messages in a queue, there is a gap of more than 3us between packets, which is too long. Can we optimize this gap.

[dmiller-nmap]

There are still optimizations that could be made to Npcap's packet injection code. Some examples:

• Create API calls for non-blocking packet writes #747 - API changes to make better use of asynchronous I/O.
• Potentially combining packets into a single NET_BUFFER_LIST (NBL) chain to reduce the overhead of calling NDIS functions for each packet.
• Keeping a pool of preallocated NBLs for write operations: https://learn.microsoft.com/en-us/answers/questions/2263145/ndis-driver-performance-and-allocation-of-net-buff

Not sure what degree of priority should be assigned to these.