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/Cargo.toml

@@ -13,8 +13,6 @@ all-features = true
 rustdoc-args = ["--cfg", "docsrs"]
 
 [dependencies]
-thiserror = { version = "1", optional = true }
-
 scale = { package = "parity-scale-codec", version = "3", default-features = false, features = ["derive", "max-encoded-len"] }
 scale-info = { version = "2", default-features = false, features = ["derive"] }
 
@@ -36,8 +34,6 @@ validator-sets-pallet = { package = "serai-validator-sets-pallet", path = "../..
 
 [features]
 std = [
-  "thiserror",
-
   "scale/std",
   "scale-info/std",