Start handling P2P messages

This defines the tart of a very complex series of locks I'm really unhappy
with. At the same time, there's not immediately a better solution. This also
should work without issue.

coordinator/tributary/src/blockchain.rs

@@ -84,10 +84,6 @@ impl<D: Db, T: Transaction> Blockchain<D, T> {
     res
   }
 
-  pub(crate) fn genesis(&self) -> [u8; 32] {
-    self.genesis
-  }
-
   pub(crate) fn tip(&self) -> [u8; 32] {
     self.tip
   }