Improve mirroring for high stress

[Razz4780]

Closes #2529

1. TcpConnectionSniffer uses broadcast channels (capacity - 512 TCP packets) to send incoming data in a non-blocking way.
2. TcpSnifferApi notifies the client about closed connection (and sends an error log) when it's broadcast::Receiver is lagging.
3. TcpConnectionSniffer notifies TcpSnifferApis about new connections via mpsc channels (capacity - 128 new sniffed connections). When a new connection is sniffed, the sniffer attempts to notify each client without blocking. If the client already has 128 queued new connections, client is not notified. There's some space for improvement here - instead of dropping new connection, we could be dropping the oldest one in the queue. However, mpsc::Sender's api does not allow for it and we would need to implement some async circular FIFO
4. BPF filter used by the raw socket is now updated only when needed - PortSubscribe/PortUnsubscribe from a user actually changed the set of subscribed ports
5. Also some minor performance optimizations like using hash_map::Entry instead of get() -> remove()

[meowjesty]

Getting rid of the nits and requests for docs first.

[meowjesty]

Just some more minor stuff, but it's worthy of approval.

Thanks for the docs, I'm happy now.

[Razz4780]

Something is not working and I don't yet know what ;/
Added some unit tests to TcpConnectionSniffer, but they all pass

[meowjesty]

👍