We have `serialize_hex` and `deserialize` but no `deserialize_hex`, add it.
Move the `IterReader` out of `consensus::serde` to the `consensus`
module.
Add some additional logic to the `DecodeError`, I'm not sure why this
wasn't there before?
Use the `HexSliceToBytesIter` by way of the `IterReader` to deserialize
an arbitrary hex string. Add unit tests to check that we consume all
bytes when deserializing a fixed size object (a transaction).
16a813734c