Replace bincode with borsh (#452)

* Add SignalsConfig to chain_spec

* Correct multiexp feature flagging for rand_core std

* Remove bincode for borsh

Replaces a non-canonical encoding with a canonical encoding which additionally
should be faster.

Also fixes an issue where we used bincode in transcripts where it cannot be
trusted.

This ended up fixing a myriad of other bugs observed, unfortunately.
Accordingly, it either has to be merged or the bug fixes from it must be ported
to a new PR.

* Make serde optional, minimize usage

* Make borsh an optional dependency of substrate/ crates

* Remove unused dependencies

* Use [u8; 64] where possible in the processor messages

* Correct borsh feature flagging

coordinator/src/tests/tributary/dkg.rs

@@ -10,6 +10,7 @@ use ciphersuite::{group::GroupEncoding, Ciphersuite, Ristretto};
 use frost::Participant;
 
 use sp_runtime::traits::Verify;
+use serai_client::validator_sets::primitives::KeyPair;
 
 use tokio::time::sleep;
 
@@ -279,7 +280,7 @@ async fn dkg_test() {
   OsRng.fill_bytes(&mut substrate_key);
   let mut network_key = vec![0; usize::try_from((OsRng.next_u64() % 32) + 32).unwrap()];
   OsRng.fill_bytes(&mut network_key);
-  let key_pair = (serai_client::Public(substrate_key), network_key.try_into().unwrap());
+  let key_pair = KeyPair(serai_client::Public(substrate_key), network_key.try_into().unwrap());
 
   let mut txs = vec![];
   for (i, key) in keys.iter().enumerate() {