Extend BitTorrent sniffer

[MakostaDev]

Currently, the BitTorrent sniffer can only detect the BitTorrent Handshake and uTP (uTP is currently broken, but PR #6667 fixes it).

I decided to add detection for several protocols from the BitTorrent family:

• UDP Tracker (BEP15)
• DHT (BEP5 & BEP42)
• LSD (BEP14)

Also string(b[1:20]) in SniffBittorrent() causes an allocation. It was replaced with bytes.HasPrefix.

I tested this using Wireshark and BitComet/qBittorrent

[Fangliding]

torrent sniffer 出于兼容性而保留 实际意义不大 它可以被非常轻松的绕过 所以不打算扩展
个人认为管理torrent的合理方法是封锁tracker ip和限制高位udp端口

[MakostaDev]

torrent sniffer 出于兼容性而保留 实际意义不大

@Fangliding with the help of a webhook, rules can warn/punish users who use torrents (this approach is used in the Torrent Blocker of the Remnawave Panel). And I know that it's impossible to completely block torrents.

When I checked packets from BitComet, I didn't notice a single uTP packet or BitTorrent Handshake (with default settings).

This PR just extends detection. And it contains very little code

[Chara-Freedom]

@RPRX why