cuprated: delay Tor P2P zone start until after sync

[redsh4de]

What

Delays the start of the Tor P2P zone until after the node has synchronized using clearnet

Closes #544

Why

Prevents deanonymization based on sync state

Where

• cuprated
  • main.rs - Changed startup logic to initialize clearnet seperately. Creates the Tor router delivery channels. Sets up a task that starts Tor zone after receiving the sync notification from blockchain manager.
  • p2p.rs - Split initialize_zones_p2p into two seperate clearnet/Tor zone init functions
  • blockchain
    • manager.rs - Returns the notification channel to main, passes it to the syncer.
    • syncer.rs - Changed check_behind_peers to check_sync_status, which now returns: no peers, behind peers, synced. On synced, fires the notification.
  • txpool
    • dandelion.rs - Receives Tor network interface via the tokio oneshot channel

How

1. On node start, an Arc<Notify> instance is created and used between the syncer and the Tor startup task
2. The Tor task waits on the notification that the node is synced, then initializes the Tor P2P zone. The old initialize_zones_p2p was split into two per-zone functions to enable this
3. The dandelion router receives the Tor network interface via a tokio::oneshot channel, checking for it in poll_ready(). Transaction routing works over clearnet initially and then adds Tor routing once it is available