Overhaul stats: Add announced Peer to HTTP core announce event

[josecelano]

Depends on: #1341

IMPORTANT: This has to be implemented after #1341.

I'm refactoring events to include more metadata:

pub enum Event {
    TcpAnnounce { connection: ConnectionContext },
    TcpScrape { connection: ConnectionContext },
}

It would also be convenient to include information about the announce request, in the event, like the peer.

pub enum Event {
    TcpAnnounce { connection: ConnectionContext, peer: Peer, original_peer_ip: IpAddr },
    TcpScrape { connection: ConnectionContext },
}

Where the Peer is the peer defined in primitive types.

NOTICE: The tracker might change the peer IP, depending on tracker configuration, like whether the tracker is running behind a reverse proxy or not. I have also added the original_peer_ip to the event; otherwise, that info would be lost. I want the events to have all the info needed to re-build exactly the tracker history if needed.

That's the only information that the tracker might change now. I do not think the tracker will ever change other data but maybe we should include the received peer and announce peer in the event:

pub enum Event {
    TcpAnnounce { connection: ConnectionContext, peer_announcement: Peer, peer_added: Peer },
    TcpScrape { connection: ConnectionContext },
}

cc @da2ce7