Enable Capture to be used async for both read an write

[Alexei-Kornienko]

Currently when you wrap a Capture in async stream you can use it read-only. I would like to be able to use it for both reading packed async and using sendpacket async as well.

My main goal is to write something similar to https://github.com/rodizio1/EZ-WifiBroadcast/
or https://github.com/svpcom/wfb-ng
Main idea of that projects is to use Wifi adapter in monitor mode and use this mode to convert it to general purpose radio transmitter/receiver for sending data over the air. I would like to do the same in Rust but for that I need to both send and receive packets on the same capture struct. Currently it's only possible in blocking mode

[Wojtek242]

PRs welcome :-)