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

message-queue/src/main.rs

@@ -76,7 +76,7 @@ mod binaries {
       [&[u8::try_from(domain.len()).unwrap()], domain, key.as_ref()].concat()
     }
     fn intent_key(from: Service, to: Service, intent: &[u8]) -> Vec<u8> {
-      key(b"intent_seen", bincode::serialize(&(from, to, intent)).unwrap())
+      key(b"intent_seen", borsh::to_vec(&(from, to, intent)).unwrap())
     }
     let mut db = db.write().unwrap();
     let mut txn = db.txn();