Remove tokio dependency from serai-coordinator-p2p

Re-implements tokio::mpsc::oneshot with a thin wrapper around async-channel.

Also replaces futures-util with futures-lite.

coordinator/p2p/src/lib.rs

@@ -8,10 +8,11 @@ use borsh::{BorshSerialize, BorshDeserialize};
 
 use serai_client::{primitives::NetworkId, validator_sets::primitives::ValidatorSet};
 
-use tokio::sync::oneshot;
-
 use serai_cosign::SignedCosign;
 
+/// A oneshot channel.
+pub mod oneshot;
+
 /// The heartbeat task, effecting sync of Tributaries
 pub mod heartbeat;