Implement serialization via parity's scale codec

Ideally, this would be generic. Unfortunately, the generic API serde 
doesn't natively support borsh, nor SCALE, and while there is a serde 
SCALE crate, it's old. While it may be complete, it's not worth working 
with.

While we could still grab bincode, and a variety of other formats, it 
wasn't worth it to go custom and for Serai, we'll be using SCALE almost 
everywhere anyways.

Cargo.lock

@@ -8870,6 +8870,7 @@ version = "0.1.0"
 dependencies = [
  "async-recursion",
  "async-trait",
+ "parity-scale-codec",
  "tokio",
 ]