Misc Peer sync info adjustments (#1896)

## Issue Addressed
#1856 

## Proposed Changes
- For clarity, the router's processor now only decides if a peer is compatible and it disconnects it or sends it to sync accordingly. No logic here regarding how useful is the peer. 
- Update peer_sync_info's rules
- Add an `IrrelevantPeer` sync status to account for incompatible peers (maybe this should be "IncompatiblePeer" now that I think about it?) this state is update upon receiving an internal goodbye in the peer manager
- Misc code cleanups
- Reduce the need to create `StatusMessage`s (and thus, `Arc` accesses )
- Add missing calls to update the global sync state

The overall effect should be:
- More peers recognized as Behind, and less as Unknown
- Peers identified as incompatible

beacon_node/network/src/sync/mod.rs

@@ -7,7 +7,6 @@ mod peer_sync_info;
 mod range_sync;
 
 pub use manager::{BatchProcessResult, SyncMessage};
-pub use peer_sync_info::PeerSyncInfo;
 pub use range_sync::ChainId;
 
 /// Type of id of rpc requests sent by sync