Add hook schemas with msggen and crate integration

[daywalker90]

Added schemas for:

• peer_connected
• recover
• commitment_revocation
• db_write
• invoice_payment
• openchannel
• openchannel2
• openchannel2_changed
• openchannel2_sign
• rbf_channel
• htlc_accepted
• rpc_command
• custommsg
• onion_message_recv
• onion_message_recv_secret

Two new primitives JsonObjectOrArray and JsonScalar to represent the raw json passed in rpc_command more cleanly.

Also added new ways to register hooks in cln-plugin, so you can do something like:

Builder::new(tokio::io::stdin(), tokio::io::stdout())
        .hook_typed("peer_connected", peer_connected)
        
async fn peer_connected(
    p: Plugin<()>,
    hook: events::PeerConnectedEvent,
) -> Result<PeerConnectedAction, anyhow::Error> {
    if hook.peer.direction == PeerConnectedPeerDirection::IN {
        log::info!("Got incoming peer connection");
    }
    Ok(PeerConnectedAction {
        error_message: None,
        result: PeerConnectedResult::CONTINUE,
    })
}