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

substrate/in-instructions/pallet/src/lib.rs

@@ -2,25 +2,13 @@
 #![cfg_attr(docsrs, feature(doc_auto_cfg))]
 #![cfg_attr(not(feature = "std"), no_std)]
 
-use scale::Encode;
-
 use sp_io::hashing::blake2_256;
-use sp_runtime::RuntimeDebug;
 
 use serai_primitives::{BlockHash, NetworkId};
 
 pub use in_instructions_primitives as primitives;
 use primitives::*;
 
-#[derive(Clone, Copy, Encode, RuntimeDebug)]
-#[cfg_attr(feature = "std", derive(scale::Decode, thiserror::Error))]
-pub enum PalletError {
-  #[cfg_attr(feature = "std", error("batch for unrecognized network"))]
-  UnrecognizedNetwork,
-  #[cfg_attr(feature = "std", error("invalid signature for batch"))]
-  InvalidSignature,
-}
-
 #[frame_support::pallet]
 pub mod pallet {
   use sp_std::vec;